To prevent a gap between an electrifying roller and the surface of a photoreceptor drum from fluctuating irrespectively of the changes of environ mental conditions such as temperature and humidity, etc.

Even in the case the elastic member 17 of the electrifying roller 14 and film materials 18 attached to both ends of the elastic member 17 individually expand in accordance with respective thermal expansion coefficient due to the change of the environmental condition where the electrifying roller 14 is placed, the film material 18 is constituted of a plurality of split pieces 18a, and each split piece 18a is fixed at prescribed intervals along the outer peripheral direction of the elastic member 17, the part of the elastic member 17 with the film material 18 attached thereto expands by the same extent as the electrifying effective area part Ca of the elastic member 17. Then, the gap G between the electrifying effective area part Ca of the electrifying roller 14 and the surface of the photoreceptor drum 5 can be kept nearly constant.