There is described a method of controlling the rotational peripheral speed of the rotating photoreceptor drum to make it constant. The method includes the steps of: detecting angular velocity signals by means of angular velocity detecting device disposed on an axis of the photoreceptor drum; finding deviations from a reference angular velocity, based on the angular velocity signals; storing a profile of the deviations within a one-revolution of the photoreceptor drum in a storage section, while revising the profile in real-time base; applying an arithmetic processing to an angular velocity signal detected at a current rotational-position of the photoreceptor drum by referring data included in the profile obtained in a preceding one-revolution of the photoreceptor drum; and controlling the motor, based on results of the arithmetic processing for the angular velocity signals, so as to compress the deviations from the reference angular velocity as small as possible.