A sheet folding apparatus includes: a conveying roller conveying a sheet in a predetermined conveying direction; a folding roller pair disposed downstream of the conveying roller in the conveying direction and rotating while nipping a predetermined position of the sheet to form a fold; a conveying path for conveying the sheet in the conveying direction from the conveying roller to the folding roller pair; an abutting member moving downstream in the conveying direction and abutting against the predetermined position of the sheet to bend the sheet downstream; and a loop space where the sheet is bent between the conveying roller and folding roller pair in a direction crossing the conveying direction. The folding roller pair stops while nipping a front end of the sheet fed from to form a loop of the sheet in the loop space, and the abutting member moves to abut against the loop.