A base of an arm having a driving projection at its tip is rotatably supported on a turn table. The turn table is provided with a first guide part and a second guide part, an outer edge part of the base of the arm and a first guide part are in contact with each other at a contact point, and a projection and a second guide part are in contact with each other at a contact point. While the arm rotates in a counterclockwise direction, the contact points are moved, and it is possible to prevent the center of the driving projection from largely deviating from a reference normal. Thus, even if a hub in which the position of the driving hole is shifted is mounted, the hub is not largely shifted in a rotation direction relative to a turn table.