PURPOSE: To decrease the production rate of chipping during a chemical reinforcing process for glass disks.

CONSTITUTION: When a glass disk 2 substantially vertically supported at three points 3, 4, 5 is subjected to ion exchange chemical reinforcing treatment in a fused salt, the left and right sides and bottom of the disk are supported with axially formed bodies 3, 4, 5, respectively. The bodies 3, 5 supporting the left and right sides are positioned below the center of the disk horizontally symmetrically with a central angle of 140-160 degree with respect to the center. By this method, the production rate of chipping in the outer circumference can be decreased.