There is provided a technique in which while the occurrence of a sheet jam is avoided, a pair of folding rollers for a folding process and a stapler for a staple process can be disposed to be close to each other, and a contribution can be made to the improvement of productivity. A staple unit is provided which performs a staple process to a bundle of sheets transported to a specified staple position in a sheet transport path, and staples the bundle of sheets by causing a press unit that presses a sheet surface of the bundle of sheets when the staple process is performed to cooperate with a reception unit that is disposed to face an inside of the sheet transport path through a hole provided in an inner wall of the sheet transport path and receives the bundle of sheets pressed by the press unit, and a vicinity of an upstream side edge of the reception unit in a sheet transport direction on the sheet transport path is covered by an elastic member supported by one of a wall surface of the sheet transport path and the reception unit.