PURPOSE: To removably attach a disk and center mask simultaneously to a vertically maintained holding plate for improving the efficiency of speeding up an operation by housing a center mask clamping mechanism, forming an air chamber to actuate negative pressure air and providing a vacuum type sucking part for sucking a disk.

CONSTITUTION: While a center mask 3 is clamped by a clamping mechanism 51, a disk 1 is vacuum sucked by negative pressure air through a sucking section 41, so that the disk 1 and center mask are removably attached to a vertically maintained holding plate simultaneously. Further, since the disk 1 is vacuum- sucked, dust is sucked from the disk surface and a center mask clamping mechanism 51 in an air chamber 46 by negative pressure air. Thus, the dust is not deposited on the disk surface so that the disk is maintained clean.