Sheet processing apparatus and image forming apparatus

A sheet processing apparatus for processing a sheet bundle, comprising:

• a stitching unit including a head portion for driving staples into the sheet bundle, and an anvil portion for receiving and bending said staples driven by the head portion and facing said head portion;
• feeding means for feeding the sheet bundle to a stitching position between the head portion and the anvil portion in the stitching unit;
• transport means attached to the stitching unit for transporting the same to a position perpendicular to a sheet bundle feeding direction;
• a guide member disposed between the head portion and the anvil portion for guiding the sheet bundle to the stitching position;
• and
• a supplement guide member disposed at an upstream side of the guide member in the sheet bundle feeding direction, said supplement guide member being able to retract to a position that does not hinder movement of the stitching unit when the stitching unit moves, and guiding the sheet bundle to the guide member without a leading edge of the sheet bundle touching an upstream edge of the guide member in the sheet bundle feeding direction when the sheet bundle is fed to the stitching position.