A base member includes a base groove portion, at least one base through-hole, and a first insulating sheet portion. The base groove portion is positioned on a lower surface of the base member. The base through-hole extends through the base member. The first insulating sheet portion is arranged on a bottom surface of the base groove portion. A lead wire extending from a coil is led out into the base groove portion through the base through-hole. The base through-hole includes a major axis extending in a radial direction and a minor axis extending in a circumferential direction. The base through-hole has a radial length larger than a circumferential width thereof. A portion of an edge of the first insulating sheet portion is arranged on the lower surface of the base member to intersect the major axis of the base through-hole and to cover a portion of the base through-hole.