Abstract: An intermediate portion of a low voltage power supply wire is extinguished by irradiation of a laser beam to form a wire cut portion. A different potential portion serves as the wire cut portion of the low voltage power supply wire. The distance between the end portions of a high voltage power supply wire and the low voltage power supply wire between which the potential is different is increased. An electrical short-circuit between the high voltage power supply wire and the low voltage power supply wire hardly occurs. Even when impurities invade into the gap between an insulating layer on the high voltage power supply wire and the low voltage power supply wire and a glass substrate, electrode corrosion of the high voltage power supply wire and the low voltage power supply wire can be prevented. A display failure can be prevented.