PURPOSE: To prevent jitter on an image from occurring caused by the overlapping of toner splashing due to the excess of a replenishing quantity or because a replenishing action with a transferring action in a device where the replenishing quantity of toner is calculated according to the sum of the digital data of the image.

CONSTITUTION: In the case that arithmetic replenishing time TA1 exceeds transfer paper interval time Tmax, replenishing action time TON is set as Tmax and the time being a difference between the arithmetic replenishing time and the Tmax is added and stored in a registor. As for succeeding replenishing timing that the arithmetic replenishing time is shorter than the Tmax, the replenishing action time TON is set after adding some period to the arithmetic replenishing time, and the time concerning the added period is subtracted from the registor and stored.