diff --git a/README.md b/README.md
index 61ae64c..ef89ebf 100644
--- a/README.md
+++ b/README.md
@@ -175,7 +175,7 @@ In rf, you can use [special variables](https://docs.ruby-lang.org/ja/latest/clas
 |-------|------|
 | \_  | The input chunk |
 | $\_ | Alias for \_ |
-| $F | Alias for \_ |
+| $F | It is an array that stores fields(`$F=_.split`) |
 | \_1, \_2, \_3, ... | First field, second field, third field... |
 
 ## Built-in methods
diff --git a/README_ja.md b/README_ja.md
index a9aa480..1d454b3 100644
--- a/README_ja.md
+++ b/README_ja.md
@@ -182,7 +182,7 @@ rfではRubyで定義されている[特殊変数](https://docs.ruby-lang.org/ja
 |-------|------|
 | \_  | 入力されたチャンクです |
 | $\_ | \_ のエイリアスです |
-| $F | \_ のエイリアスです |
+| $F | フィールドを格納した配列です(`$F=_.split`) |
 | \_1, \_2, \_3, ... | 1番目、2番目、3番目のフィールドです |
 
 ## 組み込みメソッド
diff --git a/mrblib/rf/container.rb b/mrblib/rf/container.rb
index 846505e..84f6eab 100644
--- a/mrblib/rf/container.rb
+++ b/mrblib/rf/container.rb
@@ -5,7 +5,8 @@ def _
     end
 
     def _=(data)
-      $F = $_ = data
+      $F = data.split
+      $_ = data
     end
 
     def string?