A tall region H is a region in which tall components 16 to 20, such as the coil 16, the motor relay 17, the power relay 18, and the capacitors 19 and 20, are mounted on the substrate 40. A switching region S is a region in which the four switching elements 11 to 14 are mounted on the substrate 40. A control region C is a region in which a control part 21 including the custom IC 22 and the microcomputer 23 is mounted on the substrate 40. In FIG. 4, an example of each of the tall region H, the switching region S, and the control region C are schematically shown by a broken line. In the first embodiment, the tall region H is provided on the surface β of the substrate 40 on the side close to the heat sink 30, while the switching region S and the control region C are provided on the surface α of the substrate 40 on the side close to the cover 50. Specifically, the tall components 16 to 20 are collectively provided in a particular portion of the surface β of the substrate 40 on the side close to the heat sink 30. The tall region H, the switching region S, the control region C, and a layout of the electronic components 11 to 23 mounted in each region are not limitative but illustrative.