PURPOSE: To securely prevent a damage to a photosensitive body, which is caused by a nerroneously inserted corona discharger.

CONSTITUTION: The guide rail 8 of a transfer charger 7 is supported by the main body of an image forming case via four connecting rods 9. By means of the connecting rods 9, the guide rail 8 can move between the operation position where the guide rail is close to the photosensitive body 5 and the separation position where it is separated from the photosensitive body 5. The guide rail 8 is provided with a stop means 10 for once stopping the transfer charger 7 inserted downstream in the direction in which the transfer charger 7 is inserted. When being inserted along the rail 8, the transfer charger 7 is guided by the rail and abuts on the abutment part 11a of a stop member 11 so that it is stopped once. When the transfer charger 7 is moved, after being stopped, in the direction in which the transfer charger 7 is inserted, the connecting rods 9 turn, and for the first time the transfer charger 7 is moved together with the guide rail 8 in the operation position where it is close to the photosensitive body.