PURPOSE: To make a lapping wheel not separated from a fork even in the case of a holder being rotated, by fixing a magnet to the fork of a lapping wheel holder.

CONSTITUTION: Rotation is given to a lapping wheel 12 held by a polishing machine as well as arranging a stone member at the specific position and the side face of the stone member is subjected to polishing by giving to this lapping wheel 12 parallel movement, forward and backward movement and vertical movement to the side face of the stone. Also, this wheel 12 is received by the fork 24 of a lapping wheel holder 3, when the lapping wheel 12 of the polishing machine is returned to the backward position of the parallel movement and replacement of the lapping wheel 12 on the polishing machine can be performed with the parallel movement of the polishing machine and the rotation of the holder 3. This lapping wheel 12 held on the fork 24 of the holder 3 is fixed with attraction by a magnet 27 and there is no generation of fall of the lapping wheel 12 at the turning time of the fork 24.