PURPOSE: To realize good transfer and separation, by lowering temporarily the transfer current, which is flowed to an image carrier by the corona discharge of a transfer charager, only when the trailing edge part of a transfer materal passes under the transfer charger.

CONSTITUTION: A transfer charge 7 and a guide plate 3 are spaced at a certain distance apart from each other, and transfer is performed in the trailing edge part of transfer paper 1 in the state where it is get out of the grounded quide plate 3, and therefore, the potantial in the trailing edge part of the transfer paper 1 becomes high, and the transfer paper 1 is brought into close contact with a drum 5. For the purpose of preventing this phenomenon, the trasnfer current is switched to a lower value just before or after the trailing edge part of the transfer paper 1 gets out of the guide plate 3, and the transfer potential is not so high. Thus, the transfer paper potential is always constant approximately, and the deficiency of discharge does not occur even if the current of a separating charger is constant, and good transfer and separation are performed.