An insert bus bar plate includes a plate-shaped resin material and a plurality of metal bus bars that are embedded within the resin material by insert molding and have a terminal part exposed to a mounting surface that is one of principal faces of the resin material. The bus bars are formed, before the insert molding, as a bus bar assembly before molding the one ends different from the terminal part of which are coupled to each other by a carrier to be cut after the insert molding. The insert bus bar plate (a substrate main body) is formed by the insert molding performed by oppositely arranging two bus bar assemblies before molding of the same shape so that two terminal parts are positioned in between two carriers.