In a laser printer, a photosensitive drum is rotated after the lapse of a period, necessary for a first cleaning bias applied to a cleaning roller to reach a set bias value after being turned on, for the start of an image forming operation. The first cleaning bias applied to the cleaning roller is turned off after a period of time has elapsed, required for a motor to stop rotating due to the inertia, after a motor signal is turned off and the image forming operation is finished.