This invention provides an electrical junction box that can restrain a temperature from increasing in a casing. An electrical junction box comprises a casing made of a synthetic resin material, a circuit board contained in the casing, semiconductor relay mounted on the circuit board, a bus bar. The bus bar is insert-molded in the casing. The bus bar includes an embedment section embedded in the casing, and a connecting section that is not embedded in the casing and thermally connected to the semiconductor relay.