To adjust the gap between a carrying belt and a pressing belt, when a booklet is carried-in and positioned, and is cut and is taken-out after cutting, by means of one driving motor in the mechanism of a cutter for positioning and cutting the booklet by holding the booklet between the carrying belt and the pressing belt.

The cutter is provided with a roller 4 to be brought into contact with the pressing belt 3, a rotary cam 10 fixed to the rotary shaft 11a of the motor 11, and link mechanisms 8, 7, 6, 5 which have a cam follower 9 to be brought into contact with the cam 10 at one end thereof, and is connected to the roller 4 at the other end thereof. When the booklet H is carried into the cutter, the abutting position of the rotary cam 10 with the cam follower 9 is set according to the thickness of the booklet H, and the roller 4 is moved upward, and the gap between the carrying belt 2 and the pressing belt 3 is adjusted so as to be slightly larger than the thickness of the booklet H. When the booklet is cut and carried out, the abutment of the rotary cam with the cam follower 9 is released, and the booklet H is pressed by the action of a force magnifying lever 12.