PURPOSE: To effectively prevent deterioration of sensitivity, and to extend life of a photoreceptor, by subjecting a both polarity chargeable photoreceptor to primary charging to a prescribed polarity, illuminating it with uniform light, and further imagewise exposing it.

CONSTITUTION: A photoreceptor 1 is subjected, e.g., to positive primary charging, and uniformly illuminated with uniform light L. When it is fatigued, positive charge remaining on the photoreceptor 1 is increased by deterioration of its sensitivity to positive charging, leaving its surface potential positive. When it is subjected to negative secondary charging, its residual positive charge does not obstruct the secondary charging. Then, it is exposed imagewise, since at that time negative charge due to the secondary charging on the areas exposed to the light L is compensated with the residual positive charge, a good electrostatic latent image can be formed in spite of fatigue of the photoconductive layer 11.