A disk holding apparatus comprising: a plurality of movable holding claws arranged uniformly spaced in a circumferential direction of a disk with a notch (1 A), each of the movable holding claws having a holding part formed on an inner end side of each of the movable holding claws and abutting onto an outer circumference of the disk; and a movable claw driving unit for moving each of the movable holding claws in a radial direction passing through a center of the disk between a holding position where the holding part of the movable holding claw abuts onto the outer circumference of the disk and a release position where the holding part goes away from the outer circumference; characterized by an inner ring rotatably supported by a board; an outer ring rotatably supported by the inner ring; and a rotation driving unit for rotating the inner ring, the movable claw driving unit rotating the outer ring relative to the inner ring in normal and reverse directions so that the each of the movable holding claws moves between the holding position and the release position; wherein the movable holding claws are biased outwardly in the radial direction by a first spring, the movable claw driving unit has: a plurality of levers rotatably supported on the outer ring in such a manner that an end of the lever abuts onto an outer end of a corresponding one of the movable holding claws; second springs, each provided between one of opposite ends of the levers and one of fixation pins provided on the outer ring, for biasing the movable holding claw inwardly in the radial direction by a biasing force stronger than a biasing force of the first spring; a connecting unit for connecting the inner ring and the outer ring and controlling a relative rotation angle of the inner ring and the outer ring; and a relative rotation generating unit for rotating the inner ring and the outer ring relative to each other. a plurality of movable holding claws arranged uniformly spaced in a circumferential direction of a disk with a notch (1 A), each of the movable holding claws having a holding part formed on an inner end side of each of the movable holding claws and abutting onto an outer circumference of the disk; and a movable claw driving unit for moving each of the movable holding claws in a radial direction passing through a center of the disk between a holding position where the holding part of the movable holding claw abuts onto the outer circumference of the disk and a release position where the holding part goes away from the outer circumference; characterized by an inner ring rotatably supported by a board; an outer ring rotatably supported by the inner ring; and a rotation driving unit for rotating the inner ring, the movable claw driving unit rotating the outer ring relative to the inner ring in normal and reverse directions so that the each of the movable holding claws moves between the holding position and the release position; wherein the movable holding claws are biased outwardly in the radial direction by a first spring, the movable claw driving unit has: a plurality of levers rotatably supported on the outer ring in such a manner that an end of the lever abuts onto an outer end of a corresponding one of the movable holding claws; second springs, each provided between one of opposite ends of the levers and one of fixation pins provided on the outer ring, for biasing the movable holding claw inwardly in the radial direction by a biasing force stronger than a biasing force of the first spring; a connecting unit for connecting the inner ring and the outer ring and controlling a relative rotation angle of the inner ring and the outer ring; and a relative rotation generating unit for rotating the inner ring and the outer ring relative to each other. a plurality of levers rotatably supported on the outer ring in such a manner that an end of the lever abuts onto an outer end of a corresponding one of the movable holding claws; second springs, each provided between one of opposite ends of the levers and one of fixation pins provided on the outer ring, for biasing the movable holding claw inwardly in the radial direction by a biasing force stronger than a biasing force of the first spring; a connecting unit for connecting the inner ring and the outer ring and controlling a relative rotation angle of the inner ring and the outer ring; and a relative rotation generating unit for rotating the inner ring and the outer ring relative to each other.