Abstract: Disclosed is an electromagnetically driven device for a camera so designed that an exposure control blade opening and closing sector ring, serving as rotor on the base plate of which sector ring conductor coil patterns are arranged, is arranged in a magnetic gap, the base plate of the sector ring as rotor is constituted with a thin heat setting resin plate, the conductor coil patterns are formed on both surfaces of the base plate, then the surfaces of the base plate are coated with dry film layers consisting of the ray radiation setting resin, then the coated layers are hardened with the ray radiation and then the polymerization of the base plate resin material is promoted by heat treating the above base plate.