PURPOSE: To make it possible to sort sheets by making a movable rotary body abut against a conveyer rotary body with the use of a drive means so as to clamp only one side of a sheet when the first or final one of a series of sheets is discharged.

CONSTITUTION: When a sheet S' on which the final one of a bundle of originals has been copied is discharged, a control circuit turns off a solenoid 21 so that an arm 19 is rotated in the direction B by means of a spring so as to allow dog-up roller 20 to make press-contact with a conveyer roller 16. Accordingly, the sheet S' discharged from a pair of discharge rollers 5 is clamped between and conveyed by the conveying roller 16 and the dog-up roller 20 at the left side thereof as viewed in the conveying direction, and is therefore discharged onto a paper discharge tray 7 at a position C which is different from the position where sheets S are aligned and stacked previously. Subsequently, stacking is made similarly for the second bundle of originals. Thus, it is possible to sort sheets with the use of a simple device.