Among the two main surfaces of the substrate 30, the surface facing the motor 80 (i.e., the motor side surface) on which the soldering work is performed is referred to as a first surface 301, and the other surface opposite the motor 80, that is, the surface facing away from the motor 80, is referred to as a second surface 302. The layers of the substrate 30 are referred to as a first layer L11, a second layer L12, a third layer L13, and a fourth layer L14. The layers are arranged in ascending order from the first surface 301 with the first layer L11 disposed closest to the motor 80. A first circuit pattern 41 is formed on the first layer L11, a second circuit pattern 42 is formed on the second layer L12, a third circuit pattern 43 is formed on the third layer L13, and a fourth circuit pattern 44 is formed on the fourth layer L14. An interlayer insulating layer 49 is formed between the circuit patterns 41, 42, 43, and 44 (i.e., 41-44). A surface resist layer 47 is formed on the first surface 301, and a surface resist layer 48 is formed on the second surface 302.

As shown in FIGS. 2 and 3, switching elements 121 and 221, a rotation angle sensor 25, and a custom integrated circuit (IC) (not shown) that form a drive circuit are mounted on the first surface 301 of the substrate 30. The rotation angle sensor 25 is mounted at a position facing the magnet 875 so as to detect changes in the magnetic field caused by the rotation of the magnet 875.