There are provided a plurality of pressing members (2) provided in the radial state with the tips oriented to a central axis (O) of a substrate (1) capable of moving back and forth the tips to and from the central axis (O) on a prespecified plane; a rotational body (3) rotatably provided on the substrate (1) around the central axis (O); and driven units (25, 32) for moving forward tips of the pressing members (2) toward the central axis (O) in association with rotation of the rotational body (3) to apply force to the ring with the tips of the pressing members (2) from outside of the ring. In this state, force is applied to the ring with the tips moving forward from outside of the ring. Furthermore, hooking units (16, 26) for hooking the ring on the tips are provided. In addition, a holding unit (7) is provided for positioning and holding a mounting body against the central axis (O).