PURPOSE: To make it possible to hold a recording disk of a small diameter at a prescribed height location and without an inclination in an excellent condition even if this recording disk has a projected line part.

CONSTITUTION: A small diameter disk placing part 11 where a small diameter disk 102 is placed for which a centering is performed by a small centering member 9 is made to project to upper side than a large diameter disk placing part 12 where a large diameter disk is placed for which the centering is performed by a large diameter centering member 10. Thus, even if a projected line part is on outer peripheral side than the part to be placed of the small diameter disk 102, this projected line part is not made to be abutted on the large diameter disk placing part 12.