To stabilize a disk clamping operation by operating a clamping section by a small operating force, preventing the damaging of an elastic member and a magnet and keeping constant the attracting force of the magnet even when the clamping section is fixed on a turntable in the state of no disks.

This device is provided with an elastic member 3 connected to a clamp ring 2 to support a movable part 4 and apply an elastic force to the movable part 4 so as to counter the force of attracting a magnet 14 in the movable part to a turntable 12, a position regulating section 5 provided in the clamp ring 2 to be abutted on the turntable 12 when the movable part 4 is moved to the turntable side in the state of no disks thereon. Even when a clamping part is operated in the state of no disks, since the position regulating section of the clamp ring is abutted on the turntable to permit the movement of only the movable part, the elastic member is caused to generate an elastic force by further moving the movable part, and thus the clamping part is operated by a small operating force.