PURPOSE: To prolong the life of a photoreceptor which has been discarded as the one having terminated of its life, by leaving the photoreceptor in the dark thereby making it recover from fatigue.

CONSTITUTION: A drumlike photoreceptor 1 is formed by the 1st segment (a) and the 2nd segment (b). When the performance of the 1st segment (a) has lowered owing to its reiterative use, the photoreceptor 1 is rotated in excess by 180° to put the 2nd segment 1b in a ready to use state. Since it turns out that during the use of the 2nd segment 1b the 1st segment 1a is left in the dark, it recovers from fatigue. When the performance of the 2nd segment has lowered, again the 1st segment 1a is put in a ready to use state in a similar manner. Thereafter, this is repeated. With such constitution, the life of the photoreceptor may be prolonged considerably.