To provide a sheet processing device which prevents a binding position from being shifted relative to one end of a bundle of sheets and an image forming apparatus.

A gripper unit 40 moves a bundle of sheets in a width direction perpendicular to a sheet conveying direction and conveys it to a position at which a stapler unit 41 stapling a plurality of positions in the width direction of one end portion of the bundle of sheets aligned by an alignment part performs binding processing. When a first binding position differs from the next binding position of the stapler unit 41 relative to one end of the bundle of sheets, a controller controls a gripper unit 40 so as to convey the bundle of sheets to a position at which the next binding position is identical to the first binding position relative to one end of the bundle of sheets before the next binding operation.