PURPOSE: To prevent the size of an original which can be copied from being limited to the diameter of an original cylinder by varying the rotating speed of the original cylinder in one process according to the size of the original.

CONSTITUTION: When a both-surface copy mode is set with a mode key, an original inverting solenoid is turned on in the initial process and the original is discharged to an original tray 7 in the 2nd process so that the surface opposite from the surface processed in the initial process faces an exposure platen 2. Then, the initial and the 2nd processes are carried out for each original to copy images on both surfaces of the original. Further, when the original length is longer than the circumference of the original cylinder 1, the cylinder 1 is rotated once more in the processes regarding respective originals to make the rotational distance of the peripheral surface of the cylinder 1 in the processes longer than the original length. Consequently, the size of an original is not limited to the diameter of the cylinder 1 and both-surface copying operation is facilitated.