Sheet processing apparatus and image forming system

A sheet processing apparatus for performing folding processing such that after a first folding processing is performed, a second folding processing is performed at a position different from a folding line formed at the first folding processing, and then a further folding processing is performed so that one end portion of the sheet at the first folding processing exists inside the sheet folded at the second folding processing, comprising:

• a transport path including a guide face to guide a transported sheet;
• a transport section adapted to be able to transport the sheet in a first direction for drawing the sheet transported to the transport path, and in a second direction for switching back the drawn sheet in a direction opposite to the direction for drawing;
• a rotating body pair adapted to nip the sheet transported to the transport path by a nip portion to rotate, to thereby perform folding processing on the sheet, each of the rotating body pair including a first circumferential surface with a radius from a rotating shaft of the rotating body to a rotating body circumferential surface, and a second circumferential surface with a radius from the rotating shaft smaller than the radius of the first circumferential surface;
• a folding blade adapted to push the sheet transported to the transport path to the nip portion of the rotating body pair;
• and
• a press member adapted to press one end portion of the sheet, which is subjected to the folding processing by the rotating body pair and is transported in the second direction, to guide, including a press portion adapted to press the one end portion of the sheet subjected to the folding processing by the rotating body pair in a direction in which another end portion of the sheet exists in the transport path in switching back, and a guide portion adapted to guide the sheet pressed by the press portion to the guide face of the transport path where the other end portion of the sheet exists.