diff --git a/README.md b/README.md
index c87e85c..c873819 100644
--- a/README.md
+++ b/README.md
@@ -65,7 +65,8 @@ options:
                         user_session cookie value (string or filepath)
   -n, --netrc           use .netrc authentication
   -q, --quiet           suppress output to console
-  -l, --log             log output to file
+  -l [PATH], --log [PATH]
+                        log output to file
   -v, --version         show program's version number and exit
 
 download options:
diff --git a/README_JA.md b/README_JA.md
index 045410a..dd7b78a 100644
--- a/README_JA.md
+++ b/README_JA.md
@@ -65,7 +65,8 @@ options:
                         user_session クッキー値 (文字列またはファイルパス)
   -n, --netrc           .netrcを認証に利用
   -q, --quiet           コンソールに出力しない
-  -l, --log             ファイルにログ出力
+  -l [PATH], --log [PATH]
+                        ファイルにログ出力
   -v, --version         プログラムのバージョン情報を表示
 
 download options:
diff --git a/nndownload/nndownload.py b/nndownload/nndownload.py
index 4863ab1..ff7a4ac 100644
--- a/nndownload/nndownload.py
+++ b/nndownload/nndownload.py
@@ -186,7 +186,7 @@
 cmdl_parser.add_argument("--session-cookie", dest="session_cookie", metavar="COOKIE", help="user_session cookie value (string or filepath)")
 cmdl_parser.add_argument("-n", "--netrc", action="store_true", dest="netrc", help="use .netrc authentication")
 cmdl_parser.add_argument("-q", "--quiet", action="store_true", dest="quiet", help="suppress output to console")
-cmdl_parser.add_argument("-l", "--log", nargs="?", const=f"[{MODULE_NAME}] {time.strftime('%Y-%m-%d')}.log", dest="log", metavar="[PATH]", help="log output to file")
+cmdl_parser.add_argument("-l", "--log", nargs="?", const=f"[{MODULE_NAME}] {time.strftime('%Y-%m-%d')}.log", dest="log", metavar="PATH", help="log output to file")
 cmdl_parser.add_argument("-v", "--version", action="version", version=CMDL_VERSION)
 cmdl_parser.add_argument("input", action="store", nargs="*", help="URLs or files")