PURPOSE:To prevent occurrence of dark developed portion in the periphery of the image of subject, by disposing a plurality of destaticizing lamps in the widthwise direction of photoreceptor, controlling the illumination according to the copy size, and destaticizing the both side regions and front and rear regions of the effective image region of the photoreceptor. CONSTITUTION:A destaticizing device consists of a plurality of lamps L1 to L7 which are provided in a lamp casing 20 of which length is nearly equal to the image effective width of a photoreceptor. Lamps are disposed in accordance with copy sizes on the photoreceptor surface, and are partitioned by light shielding walls 23 to 26, so that the light interference among lamps is prevented. The number of lamps and the illumination thereof are determined in relation to the copy size, distance between the destaticizing device and the photoreceptor surface, and other factors. In the case of width W1 of the effeftive image region, all lamps are lit for the period of A-A1, and B1-B. In the case of width W2 of the effective image region, lamps L1 and L7 are illuminated for the period of A-B in both end regions to destaticize, while lamps L2 to L6 are illuminated for the period of A-A2 and B2-B in the front and rear regions.