After clean-installing Mac and installing Homebrew, the following error occurred:

Warning: Now install Xcode: http://developer.apple.com/technologies/xcode.html

The cause was that Xcode wasn’t installed, so I installed Xcode from the App Store.

By the way, please refer to this for the Homebrew installation method:

・Installation method: [Mac] Installing Homebrew

That’s all.

【Reference】

・I Installed Homebrew | blog.tokuda109.jp

That’s all from the Gemba.