A sheet processing apparatus includes a conveying portion, a conveying path, a discharge port, a stacking portion, a manual setting portion, a binding device which binds a sheet bundle formed by the stacking portion and a sheet bundle set at the manual setting portion by a staple, a first regulating portion which regulates a position of the sheet bundle at a rear side of the apparatus in a width direction, and a second regulating portion which regulates a position of the sheet bundle in the conveying direction. The binding device is formed to be movable back and forth to a front side and the rear side of the apparatus. When a staple is replenished to the binding device, the binding device is positioned at the third position so that a cartridge of the staple is loaded into the binding device from the front side of the apparatus.