A base member includes a recessed portion arranged to extend in radial directions and recessed upward from a lower surface of the base member, the radial directions being directions perpendicular to a vertical direction or directions parallel to these directions; and a hole portion arranged to pass through the recessed portion in the vertical direction. The recessed portion includes a recessed portion loop-shaped surface being a loop-shaped surface perpendicular to the vertical direction. A connector is arranged on a lower side of the recessed portion to cover the hole portion. An adhesive is arranged between the connector and the recessed portion. A minimum value of a gap distance between an outer end of the connector and an inner end of the recessed portion in a radial direction in which the outer end of the connector and the inner end of the recessed portion are opposed to each other with the adhesive therebetween is greater than a minimum value of a gap distance between an upper surface of the connector and the recessed portion loop-shaped surface in the vertical direction, in which the upper surface of the connector and the recessed portion loop-shaped surface are opposed to each other with the adhesive therebetween.