PURPOSE: To permit even a member having a high hardness to be worked in high efficiency by allowing the grinding grains in minute power form which has an average particle diameter smaller than media power form which has an average particle diameter smaller than media to exist in mixed state in a barrel and adding surfactants into a working liquid.

CONSTITUTION: When a rotary barrel 1 charged with a mass 2 is revolved in the direction of arrow 7, the mass 2 flows in the direction of arrow 8, and media 3 and workpieces 4 collide each other during flowing of the mass 2, and the surface of the workpiece 4 is polished, and the grinding-grain part of the media 3 which acts as cutting edge is worn-out through polishing, and edge destruction is generated, and scarps are piled to generate clogging. Since the scraps are removed by minute powder 6, and the grinding grains which are edge-destructed are easily dropped-off, new grinding-grain parts are formed from the media 3, and the polishing force can be kept constant for a long period. Since a working liquid 5 contains surfactants, the minute powders 6 are dispersed uniformly into the whole mass 2, and the effect can be developed sufficiently, and the efficiency can be improved.