diff --git a/systems/application/application-administration-adapter-out/BUILD.bazel b/systems/application/application-administration-adapter-out/BUILD.bazel
index dd8554b9..cb35f9ec 100644
--- a/systems/application/application-administration-adapter-out/BUILD.bazel
+++ b/systems/application/application-administration-adapter-out/BUILD.bazel
@@ -4,6 +4,15 @@ load(":deps.bzl", "MODULE_DEPS", "TEST_DEPS")
 
 package(default_visibility = ["//visibility:public"])
 
+kt_jvm_test(
+    name = "kakao_distance_test",
+    srcs = ["src/test/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapterTest.kt"],
+    javac_opts = "//:javac_options",
+    kotlinc_opts = "//:kotlinc_options",
+    test_class = "hs.kr.entrydsm.application.administration.adapterout.distance.KakaoDistanceAdapterTest",
+    deps = MODULE_DEPS + TEST_DEPS + [":main"],
+)
+
 kt_jvm_test(
     name = "first_screening_mysql_concurrency_test",
     tags = ["manual"],
diff --git a/systems/application/application-administration-adapter-out/deps.bzl b/systems/application/application-administration-adapter-out/deps.bzl
index 044f18b9..bbea9913 100644
--- a/systems/application/application-administration-adapter-out/deps.bzl
+++ b/systems/application/application-administration-adapter-out/deps.bzl
@@ -28,6 +28,8 @@ KOTLIN_DEPS = [
 ]
 
 TEST_DEPS = [
+    "@maven//:ch_qos_logback_logback_classic",
+    "@maven//:ch_qos_logback_logback_core",
     "//systems/application/application-administration-application:main",
     "@maven//:org_springframework_spring_test",
     "@maven//:org_springframework_boot_spring_boot_data_jpa_test",
diff --git a/systems/application/application-administration-adapter-out/src/main/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapter.kt b/systems/application/application-administration-adapter-out/src/main/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapter.kt
index 57e33e46..217a8e96 100644
--- a/systems/application/application-administration-adapter-out/src/main/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapter.kt
+++ b/systems/application/application-administration-adapter-out/src/main/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapter.kt
@@ -3,15 +3,19 @@ package hs.kr.entrydsm.application.administration.adapterout.distance
 import hs.kr.entrydsm.admin.domain.enum.ErrorCode
 import hs.kr.entrydsm.admin.domain.exception.AdminDomainException
 import hs.kr.entrydsm.admin.domain.port.out.DistancePort
+import java.io.IOException
 import java.net.URI
 import java.net.URLEncoder
 import java.net.http.HttpClient
 import java.net.http.HttpRequest
 import java.net.http.HttpResponse
+import java.net.http.HttpTimeoutException
 import java.nio.charset.StandardCharsets
 import java.time.Duration
+import org.slf4j.LoggerFactory
 import org.springframework.beans.factory.annotation.Value
 import org.springframework.stereotype.Component
+import tools.jackson.core.JacksonException
 import tools.jackson.databind.ObjectMapper
 
 @org.springframework.boot.autoconfigure.condition.ConditionalOnProperty(name = ["application.administration.enabled"], havingValue = "true")
@@ -24,40 +28,68 @@ class KakaoDistanceAdapter(
     @Value("\${admin.maps.school-address}") private val schoolAddress: String,
     @Value("\${admin.maps.timeout-ms}") private val timeoutMs: Long,
 ) : DistancePort {
+    private val logger = LoggerFactory.getLogger(javaClass)
     private val client = HttpClient.newBuilder().connectTimeout(Duration.ofMillis(timeoutMs)).build()
-    private val schoolCoordinates by lazy { geocode(schoolAddress) }
+    private val schoolCoordinates by lazy { geocode(schoolAddress, "SCHOOL_GEOCODING") }
 
-    override fun distanceFromSchool(address: String): Long =
-        try {
-            val origin = geocode(address)
+    // 외부 응답과 예외 메시지 대신 단계와 안전한 원인만 남긴다.
+    override fun distanceFromSchool(address: String): Long {
+        var stage = "APPLICANT_GEOCODING"
+        return try {
+            val origin = geocode(address, stage)
+            stage = "SCHOOL_GEOCODING"
             val destination = schoolCoordinates
+            stage = "DIRECTIONS"
             val response = send(
                 "$directionsUrl?origin=${origin.x},${origin.y}&destination=${destination.x},${destination.y}&summary=true",
+                stage,
             )
             parseDistance(response)
-        } catch (_: Exception) {
-            unavailable()
+        } catch (exception: AdminDomainException) {
+            throw exception
+        } catch (exception: Exception) {
+            val reason = when (exception) {
+                is JacksonException -> "JSON_PARSING"
+                is HttpTimeoutException -> "TIMEOUT"
+                is IOException -> "NETWORK"
+                else -> "UNEXPECTED"
+            }
+            unavailable(stage, reason, exceptionClass = exception.javaClass.name)
         }
+    }
 
+    // 카카오의 경로 결과 코드와 거리 필드 실패를 구분한다.
     fun parseDistance(body: String): Long {
         val route = objectMapper.readTree(body).path("routes").path(0)
-        if (route.path("result_code").asInt(-1) != 0 || !route.path("summary").path("distance").canConvertToLong()) {
-            unavailable()
+        val resultCode = route.path("result_code").asInt(-1)
+        if (resultCode != 0) {
+            unavailable("DIRECTIONS", "ROUTE_RESULT", resultCode = resultCode)
+        }
+        if (!route.path("summary").path("distance").canConvertToLong()) {
+            unavailable("DIRECTIONS", "DISTANCE_MISSING")
         }
         return route.path("summary").path("distance").asLong()
     }
 
-    fun parseCoordinates(body: String): Coordinates {
-        val document = objectMapper.readTree(body).path("documents").path(0)
-        val x = document.path("x").asText().toDoubleOrNull() ?: unavailable()
-        val y = document.path("y").asText().toDoubleOrNull() ?: unavailable()
+    // 기존 좌표 파싱 호출 인터페이스를 유지한다.
+    fun parseCoordinates(body: String): Coordinates = parseCoordinates(body, "APPLICANT_GEOCODING")
+
+    // 검색 결과 없음과 좌표 형식 오류를 구분한다.
+    private fun parseCoordinates(body: String, stage: String): Coordinates {
+        val documents = objectMapper.readTree(body).path("documents")
+        if (documents.isArray && documents.isEmpty) unavailable(stage, "EMPTY_SEARCH")
+        val document = documents.path(0)
+        val x = document.path("x").asText().toDoubleOrNull() ?: unavailable(stage, "COORDINATE_FORMAT")
+        val y = document.path("y").asText().toDoubleOrNull() ?: unavailable(stage, "COORDINATE_FORMAT")
         return Coordinates(x, y)
     }
 
-    private fun geocode(address: String): Coordinates =
-        parseCoordinates(send("$geocodingUrl?query=${encode(address)}"))
+    // 주소는 요청에만 사용하며 로그에 남기지 않는다.
+    private fun geocode(address: String, stage: String): Coordinates =
+        parseCoordinates(send("$geocodingUrl?query=${encode(address)}", stage), stage)
 
-    private fun send(url: String): String {
+    // HTTP 실패 시 본문과 URL을 제외한 상태 코드만 기록한다.
+    private fun send(url: String, stage: String): String {
         val request = HttpRequest.newBuilder()
             .uri(URI.create(url))
             .timeout(Duration.ofMillis(timeoutMs))
@@ -65,13 +97,27 @@ class KakaoDistanceAdapter(
             .GET()
             .build()
         val response = client.send(request, HttpResponse.BodyHandlers.ofString())
-        if (response.statusCode() !in 200..299) unavailable()
+        if (response.statusCode() !in 200..299) unavailable(stage, "HTTP_FAILURE", httpStatus = response.statusCode())
         return response.body()
     }
 
+    // 기존 검색어 인코딩을 유지한다.
     private fun encode(value: String) = URLEncoder.encode(value, StandardCharsets.UTF_8)
 
-    private fun unavailable(): Nothing = throw AdminDomainException(ErrorCode.DISTANCE_SERVICE_UNAVAILABLE)
+    // 허용한 진단 필드만 기록하고 기존 외부 오류 계약을 유지한다.
+    private fun unavailable(
+        stage: String,
+        reason: String,
+        httpStatus: Int? = null,
+        resultCode: Int? = null,
+        exceptionClass: String? = null,
+    ): Nothing {
+        logger.error(
+            "Kakao distance failure [stage={}, reason={}, httpStatus={}, resultCode={}, exceptionClass={}]",
+            stage, reason, httpStatus, resultCode, exceptionClass,
+        )
+        throw AdminDomainException(ErrorCode.DISTANCE_SERVICE_UNAVAILABLE)
+    }
 
     data class Coordinates(val x: Double, val y: Double)
 }
diff --git a/systems/application/application-administration-adapter-out/src/test/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapterTest.kt b/systems/application/application-administration-adapter-out/src/test/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapterTest.kt
index 0bc482d9..2b8501bc 100644
--- a/systems/application/application-administration-adapter-out/src/test/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapterTest.kt
+++ b/systems/application/application-administration-adapter-out/src/test/kotlin/hs/kr/entrydsm/application/administration/adapterout/distance/KakaoDistanceAdapterTest.kt
@@ -4,6 +4,14 @@ import hs.kr.entrydsm.admin.domain.exception.AdminDomainException
 import org.junit.Assert.*
 import org.junit.Test
 import tools.jackson.databind.ObjectMapper
+import ch.qos.logback.classic.Logger
+import ch.qos.logback.classic.spi.ILoggingEvent
+import ch.qos.logback.core.read.ListAppender
+import com.sun.net.httpserver.HttpServer
+import hs.kr.entrydsm.admin.domain.enum.ErrorCode
+import java.net.InetSocketAddress
+import java.util.concurrent.atomic.AtomicInteger
+import org.slf4j.LoggerFactory
 
 class KakaoDistanceAdapterTest {
     @Test
@@ -29,4 +37,162 @@ class KakaoDistanceAdapterTest {
         assertFalse(exception?.message.orEmpty().contains("super-secret"))
     }
 
+    @Test
+    fun successfulCallsReuseLazySchoolCoordinates() = withServer { base, requests ->
+        val adapter = adapter(base)
+        capture { logs ->
+            assertEquals(1234L, adapter.distanceFromSchool(ADDRESS))
+            assertEquals(1234L, adapter.distanceFromSchool(ADDRESS))
+            assertEquals(5, requests.get())
+            assertTrue(logs.list.isEmpty())
+        }
+    }
+
+    @Test
+    fun httpFailuresIdentifyEachStageWithoutSensitiveResponse() {
+        for ((index, stage) in STAGES.withIndex()) {
+            withServer(failedRequest = index, status = 401, body = PRIVATE_BODY) { base, _ ->
+                capture { logs ->
+                    assertUnavailable { adapter(base).distanceFromSchool(ADDRESS) }
+                    assertDiagnostic(logs, stage, "HTTP_FAILURE", "httpStatus=401")
+                }
+            }
+        }
+    }
+
+    @Test
+    fun emptySearchIdentifiesApplicantAndSchool() {
+        for ((index, stage) in STAGES.take(2).withIndex()) {
+            withServer(failedRequest = index, body = """{"documents":[],"private":"$PRIVATE_BODY"}""") { base, _ ->
+                capture { logs ->
+                    assertUnavailable { adapter(base).distanceFromSchool(ADDRESS) }
+                    assertDiagnostic(logs, stage, "EMPTY_SEARCH")
+                }
+            }
+        }
+    }
+
+    @Test
+    fun routeFailureRecordsOnlyNumericCode() = withServer(
+        failedRequest = 2,
+        body = """{"routes":[{"result_code":104,"result_msg":"$PRIVATE_BODY"}]}""",
+    ) { base, _ ->
+        capture { logs ->
+            assertUnavailable { adapter(base).distanceFromSchool(ADDRESS) }
+            assertDiagnostic(logs, "DIRECTIONS", "ROUTE_RESULT", "resultCode=104")
+        }
+    }
+
+    @Test
+    fun malformedJsonRecordsExceptionClassWithoutBody() {
+        for ((index, stage) in STAGES.withIndex()) {
+            withServer(failedRequest = index, body = PRIVATE_BODY) { base, _ ->
+                capture { logs ->
+                    assertUnavailable { adapter(base).distanceFromSchool(ADDRESS) }
+                    assertDiagnostic(logs, stage, "JSON_PARSING", "exceptionClass=tools.jackson.")
+                }
+            }
+        }
+    }
+
+    @Test
+    fun timeoutRecordsStageAndExceptionClass() = withServer(delayMs = 500) { base, _ ->
+        capture { logs ->
+            assertUnavailable { adapter(base, timeoutMs = 100).distanceFromSchool(ADDRESS) }
+            assertDiagnostic(logs, "APPLICANT_GEOCODING", "TIMEOUT", "exceptionClass=java.net.http.Http")
+        }
+    }
+
+    @Test
+    fun invalidCoordinatesAndMissingDistanceHaveSeparateReasons() {
+        for ((index, body, reason) in listOf(
+            Triple(0, """{"documents":[{"x":"$PRIVATE_BODY","y":"36.3"}]}""", "COORDINATE_FORMAT"),
+            Triple(2, """{"routes":[{"result_code":0,"summary":{}}]}""", "DISTANCE_MISSING"),
+        )) {
+            withServer(failedRequest = index, body = body) { base, _ ->
+                capture { logs ->
+                    assertUnavailable { adapter(base).distanceFromSchool(ADDRESS) }
+                    assertDiagnostic(logs, STAGES[index], reason)
+                }
+            }
+        }
+    }
+
+    private fun adapter(base: String, timeoutMs: Long = 3000) =
+        KakaoDistanceAdapter(ObjectMapper(), KEY, "$base/geocode", "$base/directions", SCHOOL, timeoutMs)
+
+    private fun assertUnavailable(action: () -> Unit) {
+        val failure = runCatching(action).exceptionOrNull()
+        assertTrue("Expected AdminDomainException, got $failure", failure is AdminDomainException)
+        assertEquals(ErrorCode.DISTANCE_SERVICE_UNAVAILABLE, (failure as AdminDomainException).errorCode)
+        assertEquals(503, failure.errorCode.status)
+        assertNull(failure.cause)
+    }
+
+    private fun capture(action: (ListAppender<ILoggingEvent>) -> Unit) {
+        val logger = LoggerFactory.getLogger(KakaoDistanceAdapter::class.java) as Logger
+        val appender = ListAppender<ILoggingEvent>()
+        appender.start()
+        logger.addAppender(appender)
+        try {
+            action(appender)
+        } finally {
+            logger.detachAppender(appender)
+            appender.stop()
+        }
+    }
+
+    private fun assertDiagnostic(logs: ListAppender<ILoggingEvent>, stage: String, reason: String, detail: String? = null) {
+        assertEquals(1, logs.list.size)
+        val event = logs.list.single()
+        val message = event.formattedMessage
+        assertTrue(message, message.contains("stage=$stage"))
+        assertTrue(message, message.contains("reason=$reason"))
+        if (detail != null) assertTrue(message, message.contains(detail))
+        assertNull(event.throwableProxy)
+        for (secret in listOf(ADDRESS, SCHOOL, KEY, PRIVATE_BODY, "127.123456", "36.654321", "http://", "query=", "origin=")) {
+            assertFalse("Sensitive value leaked: $secret", message.contains(secret))
+        }
+    }
+
+    private fun withServer(
+        failedRequest: Int = -1,
+        status: Int = 200,
+        body: String = "",
+        delayMs: Long = 0,
+        action: (String, AtomicInteger) -> Unit,
+    ) {
+        val server = HttpServer.create(InetSocketAddress("127.0.0.1", 0), 0)
+        val requests = AtomicInteger()
+        server.createContext("/") { exchange ->
+            val index = requests.getAndIncrement()
+            try {
+                if (delayMs > 0) Thread.sleep(delayMs)
+                val payload = if (index == failedRequest) body else if (exchange.requestURI.path == "/directions") {
+                    """{"routes":[{"result_code":0,"summary":{"distance":1234}}]}"""
+                } else {
+                    """{"documents":[{"x":"127.123456","y":"36.654321"}]}"""
+                }
+                val bytes = payload.toByteArray(Charsets.UTF_8)
+                exchange.sendResponseHeaders(if (index == failedRequest) status else 200, bytes.size.toLong())
+                exchange.responseBody.use { it.write(bytes) }
+            } finally {
+                exchange.close()
+            }
+        }
+        server.start()
+        try {
+            action("http://127.0.0.1:${server.address.port}", requests)
+        } finally {
+            server.stop(0)
+        }
+    }
+
+    companion object {
+        private const val ADDRESS = "지원자-비공개주소"
+        private const val SCHOOL = "학교-비공개주소"
+        private const val KEY = "private-api-key"
+        private const val PRIVATE_BODY = "private-response-and-exception-message"
+        private val STAGES = listOf("APPLICANT_GEOCODING", "SCHOOL_GEOCODING", "DIRECTIONS")
+    }
 }