diff --git a/collection/README.md b/collection/README.md
index be7bbf5..20b2f1d 100644
--- a/collection/README.md
+++ b/collection/README.md
@@ -10,3 +10,9 @@
 
 append関数の使い方や仕組み
 
+## map.go
+
+map
+
+- mapのメンバは変数ではないのでアドレスは取れない
+- `delete(hoge, "key")` で要素の削除
diff --git a/collection/map.go b/collection/map.go
new file mode 100644
index 0000000..f975dc7
--- /dev/null
+++ b/collection/map.go
@@ -0,0 +1,50 @@
+package main
+
+import "fmt"
+
+func main() {
+	cal := map[string]int{
+		"Jan": 1,
+		"Feb": 2,
+		"Mar": 3,
+		"Apr": 4,
+		"May": 5,
+		"Jun": 6,
+		"Jul": 7,
+		"Aug": 8,
+		"Sep": 9,
+		"Oct": 10,
+		"Nov": 11,
+		"Dec": 12,
+	}
+	fmt.Printf("%+v\n", cal) // map[Apr:4 Aug:8 Dec:12 Feb:2 Jan:1 Jul:7 Jun:6 Mar:3 May:5 Nov:11 Oct:10 Sep:9]
+	fmt.Printf("%d\n", cal["Jan"]) // 1
+	fmt.Printf("%d\n", cal["hoge"]) // 0 存在しない場合はゼロ値
+	fmt.Printf("%d\n", len(cal)) // 12
+	fmt.Println()
+
+	for name, num := range cal {// 準不定
+		fmt.Printf("%d: %s\n", num, name)
+	}
+	fmt.Println()
+
+	v1 := map[string]int{}
+	v1["hoge"] = 100
+	v1["fuga"] = 0
+	{
+		v, ok := v1["hoge"]
+		fmt.Printf("v: %d ok: %v\n", v, ok) // v: 100 ok: true
+	}
+	{
+		v, ok := v1["fuga"]
+		fmt.Printf("v: %d ok: %v\n", v, ok) // v: 0 ok: true
+	}
+	{
+		v, ok := v1["piyo"]
+		fmt.Printf("v: %d ok: %v\n", v, ok) // v: 0 ok: false
+	}
+
+	var v2 map[string]int
+	v2["fuga"] = 1 // panic
+}
+