diff --git a/src/main/java/cnu/mvc/domain/member/MemberRepository.java b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
index 1b273fc..02900fb 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberRepository.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
@@ -22,6 +22,14 @@ public Member findById(Long id) {
 
     // 구현
     public Member findByEmail(String email) {
+        // 저장소에 회원 정보 꺼냄.
+        for (Member member : store.values()) {
+            // 일치하면 반환.
+            if (member.getEmail().equals(email)) {
+                return member;
+            }
+        }
+        // 일치하지 않으면, null 반환.
         return null;
     }
 }
diff --git a/src/main/java/cnu/mvc/domain/member/MemberService.java b/src/main/java/cnu/mvc/domain/member/MemberService.java
index b8e785e..c5eab3e 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberService.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberService.java
@@ -9,13 +9,24 @@ public class MemberService {
 
     private final MemberRepository memberRepository;
 
-    public Member join(Member member){
+    public Member join(Member member) {
+        Member existingMember = memberRepository.findByEmail(member.getEmail());
+    
+        if (existingMember != null) {
+            throw new IllegalArgumentException("이미 존재하는 이메일 계정입니다.");
+        }
+    
         return memberRepository.save(member);
     }
 
     public Member validateMember(String email, String pwd) {
-        Member findMember = findById(1L);
-        return findMember;
+        Member member = memberRepository.findByEmail(email);
+    
+        if (member == null || !member.getPwd().equals(pwd)) {
+            throw new IllegalArgumentException("이메일 또는 비밀번호를 확인해주세요.");
+        }
+    
+        return member;
     }
 
     public Member findById(Long id) {