An image drum for selectively adsorbing toner in a printing apparatus is provided. A method and a configuration of ring electrodes formed on an outside of a drum body is also provided. That is, a control board is mounted inside the drum body, of which a plurality of terminals is externally exposed in the cylindrical drum body, and a photocurable resin is coated on the circumferential surface. Ring electrodes are then formed on circumferential surface of the drum body, by rotating the drum body and allowing an ultraviolet ray through the mask pattern onto the drum body to harden the liquid photocurable resin after contacting a mask-patterned mold mask to the circumferential surface of the drum body.