A base unit includes a stator and a base member including a first recess portion, a second recess portion, and at least one through-hole. The first recess portion is arranged on an upper surface of the base member to surround the hole portion and depressed toward the lower surface thereof. The second recess portion is arranged radially outward of the first recess portion and depressed toward a lower surface thereof. The through-hole is arranged inside the first recess portion to extend through the base member. The second recess portion includes a protrusion portion and a third recess portion. The protrusion portion protrudes from the lower surface of the base member toward the upper surface of the base member. The third recess portion is depressed from the lower surface of the base member toward the upper surface of the base member and positioned at the opposite side from the protrusion portion.