diff --git a/http_server/echo/main.go b/http_server/echo/main.go
index f9533fd..ab8cb0a 100644
--- a/http_server/echo/main.go
+++ b/http_server/echo/main.go
@@ -24,6 +24,7 @@ func main() {
 	e.GET("/square", squareHandler)
 	// POST Bodyの読み込み
 	e.POST("/incr", incrementHandler)
+	e.POST("/fizzbuzz", fizzbuzzHandler)
 
 	// 8080ポートで起動
 	e.Logger.Fatal(e.Start(":8080"))
@@ -50,6 +51,9 @@ func squareHandler(c echo.Context) error {
 		// 他のエラーの可能性もあるがサンプルとして纏める
 		return echo.NewHTTPError(http.StatusBadRequest, "num is not integer")
 	}
+	if num >= 100 {
+		return echo.NewHTTPError(http.StatusBadRequest, "num is over 100")
+	}
 	// fmt.Sprintfでフォーマットに沿った文字列を生成できる。
 	return c.String(http.StatusOK, fmt.Sprintf("Square of %d is equal to %d", num, num*num))
 }
@@ -62,7 +66,43 @@ func incrementHandler(c echo.Context) error {
 		return echo.NewHTTPError(http.StatusInternalServerError, "Internal Server Error")
 	}
 	counter += incrRequest.Num
-	return c.String(http.StatusOK, fmt.Sprintf("Value of Counter is %d \n", counter))
+
+	jsonMap := map[string]int{
+		"counter": counter,
+	}
+
+	return c.JSON(http.StatusOK, jsonMap)
+}
+
+func fizzbuzzHandler(c echo.Context) error {
+	fizzbuzzRequest := fizzbuzzRequest{}
+	if err := c.Bind(&fizzbuzzRequest); err != nil {
+		return echo.NewHTTPError(http.StatusInternalServerError, "Internal Server Error")
+	}
+
+	var fizzbuzz string
+	num := fizzbuzzRequest.Num
+
+	switch {
+	case num%15 == 0:
+		fizzbuzz = "FIZZ BUZZ!"
+	case num%3 == 0:
+		fizzbuzz = "FIZZ!"
+	case num%5 == 0:
+		fizzbuzz = "BUZZ!"
+	default:
+		fizzbuzz = strconv.Itoa(num)
+	}
+
+	jsonMap := map[string]string{
+		"fizzbuzz": fizzbuzz,
+	}
+
+	return c.JSON(http.StatusOK, jsonMap)
+}
+
+type fizzbuzzRequest struct {
+	Num int `json:"num"`
 }
 
 type incrRequest struct {
diff --git a/http_server/net_http/main.go b/http_server/net_http/main.go
index 15c9f10..56c62d0 100644
--- a/http_server/net_http/main.go
+++ b/http_server/net_http/main.go
@@ -24,6 +24,8 @@ func main() {
 	// POST Bodyの読み込み
 	http.HandleFunc("/incr", incrementHandler)
 
+	http.HandleFunc("/fizzbuzz", fizzbuzzHandler)
+
 	// 8080ポートで起動
 	http.ListenAndServe(":8080", nil)
 }
@@ -48,10 +50,16 @@ func squareHandler(w http.ResponseWriter, req *http.Request) {
 	num, err := strconv.Atoi(numStr)
 	if err != nil {
 		// 他のエラーの可能性もあるがサンプルとして纏める
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusMethodNotAllowed)
 		fmt.Fprint(w, "num is not integer")
 		return
 	}
+
+	if num >= 100 {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprint(w, "too many numbers lol")
+		return
+	}
 	// fmt.Sprintfでフォーマットに沿った文字列を生成できる。
 	fmt.Fprint(w, fmt.Sprintf("Square of %d is equal to %d", num, num*num))
 }
@@ -59,6 +67,11 @@ func squareHandler(w http.ResponseWriter, req *http.Request) {
 // Bodyから数字を取得してその数字だけCounterをIncrementするハンドラー
 // DBがまだないので簡易的なもの
 func incrementHandler(w http.ResponseWriter, req *http.Request) {
+	if req.Method != "POST" {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		fmt.Fprint(w, fmt.Sprintf("Only POST method is permitted\n"))
+		return
+	}
 	body := req.Body
 	// bodyの読み込みに開いたio Readerを最後にCloseする
 	defer body.Close()
@@ -74,6 +87,42 @@ func incrementHandler(w http.ResponseWriter, req *http.Request) {
 	fmt.Fprint(w, fmt.Sprintf("Value of Counter is %d \n", counter))
 }
 
+func fizzbuzzHandler(w http.ResponseWriter, req *http.Request) {
+	if req.Method != "POST" {
+		fmt.Fprint(w, fmt.Sprintf("Only POST method is permitted\n"))
+		return
+	}
+
+	body := req.Body
+	defer body.Close()
+
+	buf := new(bytes.Buffer)
+	io.Copy(buf, body)
+
+	var fizzbuzzRequest fizzbuzzRequest
+	json.Unmarshal(buf.Bytes(), &fizzbuzzRequest)
+
+	var fizzbuzz string
+	num := fizzbuzzRequest.Num
+
+	switch {
+	case num%15 == 0:
+		fizzbuzz = "FIZZ BUZZ!"
+	case num%3 == 0:
+		fizzbuzz = "FIZZ!"
+	case num%5 == 0:
+		fizzbuzz = "BUZZ!"
+	default:
+		fizzbuzz = strconv.Itoa(num)
+	}
+
+	fmt.Fprint(w, fmt.Sprintf("%s\n", fizzbuzz))
+}
+
+type fizzbuzzRequest struct {
+	Num int `json:"num"`
+}
+
 type incrRequest struct {
 	// jsonタグをつける事でjsonのunmarshalが出来る
 	// jsonパッケージに渡すので、Publicである必要がある