In a copying processing performed several times from the depression of a copy button of a copying machine until the surface potential of the photoreceptor drum (1) is stabilized, a voltage sufficiently high for correcting the rise characteristic of the photosensitive layer on the drum surface is applied to a charger (2). A main circuit (20) having a controlling portion to realize this corrects the output voltage of the high-voltage generating circuit which applies a high voltage to the charger (2) to a voltage value necessary for the drum surface to be charged at a stable potential level. The main circuit (20) charges the drum surface at the stable potential level necessary for development from copying of the first sheet. <IMAGE>
