Lower surface terminals are disposed at the lower surface of a magnetic substrate. An upper surface electrode is disposed at the upper surface of the magnetic substrate. A control circuit, an input capacitor, and an output capacitor are mounted on the upper surface electrode. The control circuit contains a switching element. A smoothing choke is disposed inside the magnetic substrate. The connection wiring of connecting the upper surface electrode and at least one of the input terminal, the output terminal, and the ground terminal is constructed using an inner conductor passing through the inside of the magnetic substrate, and the connection wiring forms an inductor.