To adhere a rear surface structure body and a mirror surface each other via one kind or only several kinds of connecting parts by adhering a face of connecting part to the rear surface structure body and the other face to the mirror surface and then mutually adhering the remaining surfaces of each connecting part.

The connecting part 8a and 8b are an example of a connecting part provided with at least two surfaces intersecting with each other 90° and an L-shaped connecting part with an angle of 90°. The rear surface structure body 4 and the part 8a are adhered with adhesives, the mirror surface 5 and the part 8b are adhered with adhesives, and the part 8a and the part 8b are adhered with adhesives. By using the connecting parts 8a and 8b like this, the body 4 and the surface 5 can indirectly be connected by the part 8a and 8b of the same shape by position deviation on the adhering surface of the part 8a and the part 8b though an angle formed by the body 4 and the surface 5 varies.