PURPOSE: To grind a workpiece without giving any defect thereto by a method wherein the workpiece is put in a mixture composed of grain pieces of synthetic rubber and the like and of the powder of a grinding material and all of these substances are made to perform relative motions mutually.

CONSTITUTION: Grain pieces 2 made of synthetic rubber, for instance, and the powder 3 of a grinding material are mixed, a workpiece 4 is put in the mixture thus made, the group of grain pieces and the workpiece 4 are made to perform relative motions mutually, and thus grinding is carried out.