PURPOSE: To eliminate the position deviation of copying paper from conveying belts and to prevent paper jamming and edge folding by applying the adequate suction force of fans to the copying paper according to its sizes.

CONSTITUTION: Plural pieces of chambers 2a, 2b are provided respectively independently, and fans 22a, 22b are provided in the respective chambers. In the case of sizes A4, B5 as a result of the detection of copying paper sizes, only the fan 22a is driven and in the case of B4, A3, both fans are driven. This results in that the copying paper of a small size is sucked by one fan and the copying paper of a large size by the plural fans and therefore the suction force suited for the sizes of the copying paper is applied upon the copying paper. In this way, the position deviation of the copying paper from conveying belts 5 is eliminated and the jamming and edge folding of the paper are prevented.