PURPOSE: To prevent a body from being deteriorated by the harmful matter generated from an electrostatic charger by putting a shutter into an open position during the rotational driving of the photosensitive body and putting the shutter into a shut position during the stop of the driving.

CONSTITUTION: The shutter 39 faces a photosensitive belt 7 and puts the surface of the belt 7 into a chargeable state while a main motor is held driven (while a driving wire 51 is held de-energized). The spacing between a grid plate 37 of the electrostatic charger and the belt 7 is held shut off by the shutter 39 while the main motor is held stopped (the driving wire 51 is held energized). The Nox sticking and remaining on the inside wall of a casing 31 of the electrostatic charger does not stick to the photosensitive belt 7 in this way even if the Nox gradually parts from the wall and falls while a laser printer is held stopped.