PURPOSE: To supply toner accurately and to correct automatically the set number of sheets to the number of sheets by which images can be formed by providing a rest calculating circuit which judges whether images can be formed by a preset number of sheets from the rest of a developer and calculates the number of sheets by which images can be formed.

CONSTITUTION: An exposing device 3 consists of a LED array 3a and a light converging lens array 3b and LEDs are turned on selectively with the signal of a driver circuit 12 which operates according to an image signal VD, thereby forming a dot type electromagnetic image on the surface of a photosensitive body 1 which is charged electrostatically and uniformly. Further, the image signal VD is sent out to a counter part 13 as a binary signal of '0' and '1' and when the signal '1', a LED illuminates to form a one-dot electrostatic latent image. When this part is a print image part, the counter part 13 counts '1' to obtain the total number of dots of one print. The output of the counter 13 is sent out to a toner consumption calculating circuit 14, and the amount of toner which is consumed by a developing device is calculated. Thus, the rest of the developing material is controlled accuately.