PURPOSE: To enable a document to be always reliably fed, by a method wherein, when a side guide member, installed to one edge of a document tray, is moved laterally according to the size of a document, a convey roller is moved to the center of the document in linkage with said movement.

CONSTITUTION: A side guide member 20 is laterally movably installed to one edge of a document tray 1. In this case, a rack 21, extending laterally through a supporting member 22, is mounted on the back of the side guide member 20, and a pair of gears 23 and 24 are pivotally secured to the back of the document tray 1. Racks 21 and 25 are engaged with the gears 23 and 24, respectively, and the rack 25 is installed to a supporting member 26 of a roller 9. Meanwhile, a convey roller 9 is located on a rotary shaft 27, extending through supporting plates, through one-way clutches 29 between a pair of said supporting plates 28 on a supporting member 26 so that said roller is axially movable within an opening 30 of an upper guide plate 14. This enables the convey roller 9 to be moved to the center of a document in linkage with movement of the side guide member 20.