Patent ID: 8246034

Claim:
A sheet processing apparatus comprising: a processing tray on which sheets conveyed from an image forming apparatus or supplied through a discharge port for manual stapling, are placed; a lateral alignment unit which has a pair of alignment boards movable in a direction orthogonal to a direction of the conveying, and holds the sheets on the processing tray between the pair of alignment boards and aligns the sheets; a damper attached to a surface of one alignment board of the pair of alignment boards that is contacted by the sheets; a sensor which operates if the damper is pushed by the sheets during alignment of the sheet; a stapler which staples sheets placed on the processing tray; a sheet discharge unit which discharges the stapled sheets from the processing tray through the discharge port; and a control unit which controls so that the sheets are stapled after an operation of closing the pair of alignment boards until operation of the sensor and then opening the pair of alignment boards, is performed plural times, when the sheets are inserted through the discharge port for manual stapling.