diff --git a/core/api_coupon.go b/core/api_coupon.go
index 1d1f4a8..23b99b7 100644
--- a/core/api_coupon.go
+++ b/core/api_coupon.go
@@ -197,7 +197,12 @@ func downloadCoupons(mongoClient gocommon.MongoClient, w http.ResponseWriter, r
 	roundnum := binary.BigEndian.Uint32(roundObj[:])
 	var coupons []string
 	for _, uid := range coupon.Remains {
-		coupons = append(coupons, makeCouponKey(roundnum, []byte(uid)))
+		decUid, err := hex.DecodeString(uid)
+		if err != nil {
+			logger.Println("downloadCoupons Fail", err)
+			continue
+		}
+		coupons = append(coupons, makeCouponKey(roundnum, decUid))
 	}
 
 	enc := json.NewEncoder(w)
@@ -274,8 +279,8 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 		round, _ = coupon.MakeCouponRoundHash(code)
 	}
 
-	// 1. 내가 이 라운드의 쿠폰을 쓴 적이 있나
-	already, err := mongoClient.Exists(CollectionCouponUse, bson.M{
+	// 쿠폰 사용 유무 검사
+	alreadyused, err := mongoClient.Exists(CollectionCouponUse, bson.M{
 		"_id":    acc,
 		"rounds": round,
 	})
@@ -285,7 +290,7 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 		return
 	}
 
-	if already {
+	if alreadyused {
 		// 이미 이 라운드의 쿠폰을 사용한 적이 있다.
 		w.WriteHeader(http.StatusConflict)
 		return
@@ -311,7 +316,8 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 	} else {
 		// 2. 쿠폰을 하나 꺼냄
 		matched, _, err := mongoClient.Update(CollectionCoupon, bson.M{
-			"_id": roundObj,
+			"_id":     roundObj,
+			"remains": key,
 		}, bson.M{
 			"$pull": bson.M{"remains": key},
 		})
@@ -339,6 +345,12 @@ func useCoupon(mongoClient gocommon.MongoClient, w http.ResponseWriter, r *http.
 		}
 	}
 
+	if coupon.Expire < time.Now().Unix() {
+		// 쿠폰 만료시간 경과
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
 	if len(coupon.Effect) == 0 {
 		// 쿠폰이 없네?
 		w.WriteHeader(http.StatusBadRequest)