Somehow, I tried to reinstall the XCode on my Macbook Air again but
I hesitated it due to the shortage of the disk space,
At that time, my colleague said I used much bigger file usage than he thought,
And told me his helpful method for detecting which directories use much.
The below method is like using ‘du’,’awk’ and his great technique.
http://tech.g.hatena.ne.jp/rx7/20150330/p1

Oh, Thanks to his help and I removed the files showed by his method.

However, the disk space didn’t increased any of a bit.
I felt strange and rerun the command again.
Then I noticed an unknown directory which hadn’t appeared before.
I googled the folder name, it was ‘/.MobileBackups’, and knew it as the directory which temporarily stored files I operate when couldn’t access my time machine.
So what I thought it as a remove was a move.
By the way I haven’t been connected to my time machine for 364 days. ^^;