To provide a sheet after-treatment device having a staple device which has an excellent conformability, and can align a sheet bundle bound corresponding to a high speed machine, without generating wrinkles slippages, and the like.

This sheet after-treatment device is provided with an exhaust roller 6 to exhaust sheets; a loading part 7 to which the exhausted sheets can move down naturally; a conforming means 10 to align by the natural moving down; a staple means 13 to bind a conformed sheet bundle; a sheet conveyer roller 12 to move the bound sheet bundle from the loading part 7 in the natural moving down direction; a sheet reversing route 15 to reverse the moved sheet bundle; an exhaust roller 16 to exhaust the reversed sheet bundle; and a loading tray to load the exhausted sheet bundle.