For a conventional image forming apparatus, since a waveform in a phase opposite that of a rotation change waveform is applied to a
drive motor to rotate a photosensitive member, a correction to cancel the rotation change is also performed for a sudden rotation change of the photosensitive member, or for a
high frequency change in the
noise component generated by a rotation
detector. As a result, since the
drive motor can not be smoothly rotated, and since the drive torque of the
drive motor is not stabilized, small vibrations always occur in the photosensitive member and cause image deterioration, such as a
jitter or banding. Therefore, according to the invention,
cycling due to the eccentricity of the photosensitive member is represented by using a continuous repetition function, and the waveform in the opposite phase is employed as a drive instruction value for the driving unit. With this arrangement, smooth rotation of the driving unit can be obtained, and the offsetting of the change is performed.