PURPOSE: To prevent the counterfeed of a discharged sheet by installing a reversefeed preventing member for sheet, close to a means for discharging the sheet after copying outside the machine or for reversely transporting the sheet for the backsurface copying or multiple copying.

CONSTITUTION: A sheet S0 transported from the upstream side after copying passes through the upper surface of a flapper 17, and said passing is detected by a sensor 32, and the sheet is discharged above a sorter 21 by the normal revolution of a normal/reverse revolution transporting means 19, and loaded onto a sheet S. When the backsurface copying or multiple copying of the sheet S0 is necessary, the normal/reverse revolution transporting means 19 is reversed, and the flapper 17 turns in the counterclockwise direction, and the sheet is reversely transported into the machine as shown by the sheet S1. A counterfeed preventing member 31 having a counterfeed preventing hook 31a is installed coaxially with a lower roller 19b, and the preceding sheet S2 having the curled lower edge is prevented from being reversely fed together with the sheet S1. Therefore, the sheets can surely be transported reversely one by one.