A power circuit section including a plurality of bus bars is disposed through an insulation layer on a circuit arrangement surface of a heat radiation member. An end of each of the bus bars is folded up from the circuit arrangement surface to form an external connection terminal. An enclosure wall member that surrounds the power circuit section including the external connection terminal is disposed on the heat radiation member. A connector housing contains an external connection connector that comprises a bottom portion provided with terminal, a through-hole into which the external connection terminal is inserted, and a hood that surrounds the external connection terminal. The external connection connector can be coupled to another connector together with the external connection terminal. A waterproof layer is formed within the enclosure wall member so that at least a part of the power circuit section is sealed and the terminal through-hole is sealed.