In the a circuit board, a plurality of conductive layer regions coated with a conductor are separately formed on both sides of an insulating substrate, the conductive layer region formed on either side of an insulating region on each of the both sides of the insulating substrate. The plurality of the conductive layer regions include a plurality of through holes which penetrate through the insulating substrate and are coated with a conductor over an inner wall, the conductor in the through hole electrically conducts the coated conductor of the plurality of the conductive layer regions, one of the lead pins is connected to one of the separated conductive layer regions on the both sides based on the insulating region, and the other lead pin is connected to the other conductive layer region.