An image drum manufacturing method including: providing a hollow cylindrical mold having a plurality of mold grooves circumferentially cut in its inner circumferential surface and a core portion having a smaller diameter than a hollow of the mold and having a slit-shaped combination groove; filling a conductive material into the mold grooves of the mold; inserting a control unit for individually applying a voltage to each terminal in the combination groove of the core portion, so that a conductive pattern corresponding to the conductive material is partially exposed; inserting the core portion into the mold so that the conductive pattern corresponds to the conductive material filled into each mold groove; and forming a drum body to be integrally formed with the control unit and the conductive material by filling a molten plastic into a space between the mold and the core portion.