diff --git a/src/main/java/life/mosu/mosuserver/application/user/MyUserService.java b/src/main/java/life/mosu/mosuserver/application/user/MyUserService.java
index f67d0fbb..027cf544 100644
--- a/src/main/java/life/mosu/mosuserver/application/user/MyUserService.java
+++ b/src/main/java/life/mosu/mosuserver/application/user/MyUserService.java
@@ -2,6 +2,7 @@
 
 import static life.mosu.mosuserver.global.util.EncodeUtil.passwordEncode;
 
+import life.mosu.mosuserver.domain.user.entity.AuthProvider;
 import life.mosu.mosuserver.domain.user.entity.UserJpaEntity;
 import life.mosu.mosuserver.domain.user.repository.UserJpaRepository;
 import life.mosu.mosuserver.global.exception.CustomRuntimeException;
@@ -42,11 +43,13 @@ public ChangePasswordResponse changePassword(ChangePasswordRequest request,
     @Transactional(readOnly = true, propagation = Propagation.SUPPORTS)
     public FindLoginIdResponse findLoginId(FindLoginIdRequest request) {
         UserJpaEntity user = userJpaRepository.findByNameAndPhoneNumber(request.name(),
-                        request.phoneNumber())
+                        PhoneNumberUtil.formatPhoneNumber(request.phoneNumber()))
                 .orElseThrow(() -> new CustomRuntimeException(ErrorCode.NOT_FOUND_LOGIN_ID));
 
+        if (user.getProvider() == AuthProvider.KAKAO) {
+            throw new CustomRuntimeException(ErrorCode.KAKAO_ACCOUNT_DUPLICATED);
+        }
         return FindLoginIdResponse.from(user.getLoginId());
-
     }
 
     @Transactional(readOnly = true, propagation = Propagation.SUPPORTS)
diff --git a/src/main/java/life/mosu/mosuserver/global/exception/ErrorCode.java b/src/main/java/life/mosu/mosuserver/global/exception/ErrorCode.java
index 88c23116..948e759e 100644
--- a/src/main/java/life/mosu/mosuserver/global/exception/ErrorCode.java
+++ b/src/main/java/life/mosu/mosuserver/global/exception/ErrorCode.java
@@ -168,6 +168,7 @@ public enum ErrorCode {
 
     // ID 찾기 관련
     NOT_FOUND_LOGIN_ID(HttpStatus.NOT_FOUND, "해당 아이디를 찾을 수 없습니다.", CriticalLevel.LOW),
+    KAKAO_ACCOUNT_DUPLICATED(HttpStatus.CONFLICT, "카카오로 가입한 사용자입니다", CriticalLevel.LOW),
 
     //결제 API 실패
     PAYMENT_API_ERROR(HttpStatus.BAD_REQUEST, "결제 API 호출에 실패하였습니다.", CriticalLevel.CRITICAL),