Sheet processing apparatus and image forming system

A sheet processing apparatus that performs fold processing in such a manner as to apply first fold processing to a sheet and then apply second fold processing at a position different from a fold line formed in the first fold processing so as to make one end of the sheet folded in the first fold processing lie inside the other end of the sheet folded in the second fold processing,

• the apparatus comprising:
• a conveying path that guides a sheet conveyed in a predetermined conveying direction;
• a position adjusting unit that has a contacting part against which a downstream side end portion in the conveying direction contacts and moves in the conveying direction and its opposite direction so as to adjust the position of the sheet;
• a grip unit configured to be movable integrally with the position adjusting unit and to grip the sheet adjusted in position by the position adjusting unit;
• a thrust member that thrusts the sheet adjusted in position by the position adjusting unit;
• a rotating body pair that rotates while pressing the sheet thrust by the thrust member at a nip part to apply fold processing to the sheet;
• and
• a control part that controls the driving of the position adjusting unit, the grip unit, the thrust member, and the rotating body pair, the control part using the rotating body pair to apply first fold processing to the sheet conveyed to the conveying path and causing the grip unit to grip a folded sheet that has been subjected to the first fold processing when the folded sheet is fed back to the conveying path by moving the position adjusting unit.