A predetermined level of voltage is applied to a transfer roller (26) to transfer a toner image on a photosensitive drum (22). After a predetermined number of recording sheets are made, a cleaning sequence is started wherein a voltage of -900V is applied as a cleaning voltage. Before applying the transfer voltage of 3kV, intermediate voltage is applied once or more under the control of a control unit (30). The control unit (30) instructs the application of the voltage through an electrical circuit (32) to the transfer roller (26) based on conditions set in a memory (33) and/or information given by a machine temperature sensor (35).