An image forming apparatus includes a developing device. The developing device includes a toner carrier (developing roller). The developing roller includes a base member, electrode bars, a pair of electrodes, and a protection layer. The base member includes a conductive core and an insulating layer formed on the outer surface of the core. The electrode bars and the pair of electrodes are made of a conductive metal, and are provided on the outer surface of the insulating layer. The electrode bars and the pair of electrodes are formed in a way that an unnecessary portion of a metal film is irradiated with a laser beam and thus is removed. The electrodes are each formed helically on the outer surface of the base member 1 and formed to taper down toward the outmost side thereof in its cross section.