PURPOSE: To enhance the movability and controllability of a side guide by providing a longitudinal slit in the side guide and by providing a guide pin for engaging with the slit, to a supporting member so that the supporting member is made to follow the guide through the engagement between the slit and the guide pin.

CONSTITUTION: A guide pin 8 screwed into a supporting member 4 is engaged with a longitudinal slit 7 in a side guide 3 with the engaging head of the guide pin 8 so that the supporting member 4 is coupled to the side guide 3 being enabled to follow up freely. In this case, the guide pin 8 is arranged to be vertically slidable along the slit 7. With this arrangement, the supporting member 4 slidingly follows the side guide 3 through the guide pin 8 when the side guide 3 is adjusted to the width of papers by guide shaft 5, so that the supporting of the under surface of the papers is held. Further, the guide pin 8 freely slides and climbs in the slit 7 when a tray 1 is raised due to the decrease in the papers. Thereby, the movability and controllability of the side guide may be enhanced.