A paper pressing unit is composed of two cylindrical paper pressing portions, connecting members to which the paper pressing portions are each connected, and rotational shafts protruding outward from the central parts of the connecting members along the longer sides thereof, and is rotatably supported between frames provided inside the apparatus and disposed in the width direction of the processing tray (in the direction perpendicular to the plane of FIG. 2). The paper pressing portions are disposed in such a way that a surface of a circular cylinder whose cylindrical axis corresponds to a line passing through the rotational shafts is divided thereby into equal parts (into two equal parts). The paper pressing portions travel on the same orbit as the paper pressing unit rotates.