PURPOSE: To certainly and easily perform operation by a method wherein a precious stone is set to an angle indexing machine and cut into a polygonal cube using a diamond wheel cutter while straightly and horizontally moved by a manual handle.

CONSTITUTION: A plurality of quartz semiprecious stones having an appropriate dimension through which a piano wire is passed are fixed to the center point at the angle, which is indexed by the angle setting shaft 2 of an angle-rotation indexing machine 1, by a fixed center disc 3 and a moving center receiver 6. At this time, the shift due to a size is adjusted by a fine adjustment device 5. Each of the quartz semiprecious stones is cut at the indexed angle by a diamond wheel cutter 8 while a moving disc 10 is horizontally and straightly moved by a manual handle 13. At this time, left and right deflections are controlled by a control plate 4. Therefore, operation can be easily performed even by an unskilled person and a polygonal cube can be ground without lowering quality.