PURPOSE: To maintain stable high image quality by preventing deterioration of print quality, such as a toner fog increase in a non-image area or print blur due to an image density decrease, accompanied with the long term use of an electrophotographic device.

CONSTITUTION: The amount of the operation of a developing device (developing means) is detected by a means B for detecting the amount of operation, and while the peripheral speed of a developing roller 13 is compared with the rotational-speed information of a memory means D according to the output of the means B, a drive means C is controlled by the rotation speed control means A and the rotation speed of the developing roller 13 is increased. Thus, because the toner carry performance of the developing roller 13 is improved according to the amount of the operation of the developing device, print blur and fog are prevented.