PURPOSE: To carry out the automatic adjustment, obviating the necessity of a jogging rod, etc., by allowing an adjusting member made of an elastic material, etc., to be engaged at one edge with a sheet and to make contact with a vertical member at the other end, when a tray vertically moves and shifts to a needle stop position.

CONSTITUTION: A tray 4a is at the execution position of a staple ring, and holds a sheet in an engagement state between the angular part 22b of a vertical member 22 and the vertical plane 20a of an adjusting member 20. Accordingly, the function for adjusting the sheet is executed by the parts 22a-22c of the vertical member 22 as adjusting member, in correspodence with the upward movement of the tray 4 during the assorting operation. In the downward movement of the tray during the assorting operation, the similar functions are executed by the lower part of the vertical member 22. Accordingly, the outwardly angular part 22c consists of a vertical connection part 22d and an inclined part 22e, and since the sheet in the tray 4c is gently regulated in the lateral direction towards the vertically opposed surface 20a, each edge part is finely adjusted between the vertical part 22f extending downward and the surface 20a of the adjusting member, and the sheet is transferred.