A belt member is seamed to form an endless belt which is stretched by a plurality of roller members and circulated in a first direction. The belt member is provided with an electrode portion at a first end portion thereof in a second direction perpendicular to the first direction. A cleaning member is abutted against the belt member. A seam of the belt member extends obliquely relative to the first direction such that an end of the seam confronting the electrode portion is situated in an upstream side of the first direction.