diff --git a/src/main/java/com/kamco/cd/kamcoback/config/resttemplate/ExternalHttpClient.java b/src/main/java/com/kamco/cd/kamcoback/config/resttemplate/ExternalHttpClient.java
index 048625a4..8c2e36b1 100644
--- a/src/main/java/com/kamco/cd/kamcoback/config/resttemplate/ExternalHttpClient.java
+++ b/src/main/java/com/kamco/cd/kamcoback/config/resttemplate/ExternalHttpClient.java
@@ -1,10 +1,14 @@
 package com.kamco.cd.kamcoback.config.resttemplate;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Component;
 import org.springframework.web.client.HttpStatusCodeException;
@@ -16,15 +20,53 @@ import org.springframework.web.client.RestTemplate;
 public class ExternalHttpClient {
 
   private final RestTemplate restTemplate;
-  private final com.fasterxml.jackson.databind.ObjectMapper objectMapper;
+  private final ObjectMapper objectMapper;
 
+  /**
+   * - responseType이 DTO면: DTO로 역직렬화 - responseType이 String.class면: 응답을 byte[]로 받아 UTF-8 원문 문자열로 반환
+   * (배열/객체 등 유동 JSON 안전)
+   */
   public <T> ExternalCallResult<T> call(
       String url, HttpMethod method, Object body, HttpHeaders headers, Class<T> responseType) {
 
-    if (headers == null) headers = new HttpHeaders();
-    headers.setContentType(org.springframework.http.MediaType.APPLICATION_JSON);
-    headers.setAccept(java.util.List.of(org.springframework.http.MediaType.APPLICATION_JSON));
+    HttpHeaders resolvedHeaders = resolveJsonHeaders(headers);
+    logRequestBody(body);
 
+    HttpEntity<Object> entity = new HttpEntity<>(body, resolvedHeaders);
+
+    try {
+      if (responseType == String.class) {
+        ResponseEntity<byte[]> res = restTemplate.exchange(url, method, entity, byte[].class);
+        String raw =
+            (res.getBody() == null) ? null : new String(res.getBody(), StandardCharsets.UTF_8);
+
+        @SuppressWarnings("unchecked")
+        T casted = (T) raw; // responseType == String.class 이므로 안전
+        return new ExternalCallResult<>(res.getStatusCodeValue(), true, casted, null);
+      }
+
+      ResponseEntity<T> res = restTemplate.exchange(url, method, entity, responseType);
+      return new ExternalCallResult<>(res.getStatusCodeValue(), true, res.getBody(), null);
+
+    } catch (HttpStatusCodeException e) {
+      return new ExternalCallResult<>(
+          e.getStatusCode().value(), false, null, e.getResponseBodyAsString());
+    }
+  }
+
+  private HttpHeaders resolveJsonHeaders(HttpHeaders headers) {
+    HttpHeaders h = (headers == null) ? new HttpHeaders() : headers;
+
+    if (h.getContentType() == null) {
+      h.setContentType(MediaType.APPLICATION_JSON);
+    }
+    if (h.getAccept() == null || h.getAccept().isEmpty()) {
+      h.setAccept(List.of(MediaType.APPLICATION_JSON));
+    }
+    return h;
+  }
+
+  private void logRequestBody(Object body) {
     try {
       if (body != null) {
         log.info("[HTTP-REQ-BODY-JSON] {}", objectMapper.writeValueAsString(body));
@@ -32,16 +74,6 @@ public class ExternalHttpClient {
     } catch (Exception e) {
       log.warn("[HTTP-REQ-BODY-JSON] serialize failed: {}", e.getMessage());
     }
-
-    HttpEntity<Object> entity = new HttpEntity<>(body, headers);
-
-    try {
-      ResponseEntity<T> res = restTemplate.exchange(url, method, entity, responseType);
-      return new ExternalCallResult<>(res.getStatusCodeValue(), true, res.getBody(), null);
-    } catch (HttpStatusCodeException e) {
-      return new ExternalCallResult<>(
-          e.getStatusCode().value(), false, null, e.getResponseBodyAsString());
-    }
   }
 
   public record ExternalCallResult<T>(int statusCode, boolean success, T body, String errBody) {}