An image forming apparatus includes an image bearing member having a conductive layer and a surface layer capable of retaining electric charge, driving device for moving the image bearing member, toner supplying device for supplying conductive or semiconductive toner to the surface layer of the image bearing member, a driver for driving the toner supplying device, electric power source for applying a bias voltage between the toner and the conductive layer of the image bearing member, and setting or control device for setting the bias voltage application to provide gradually increasing voltage at the start of the bias voltage application. The surface layer has a surface resistivity of approximately 10.sup.8 -10.sup.13 ohm/.quadrature., preferably 10.sup.9 -10.sup.12 ohm/.quadrature. and has a bulk volume resistivity of approximately 10.sup.10 -10.sup.16 ohm.cm, preferably 10.sup.10 -10.sup.13 ohm.cm.