PURPOSE: To supplement the grinding stones and the compound solution as necessary and carry out the continuous operation for a long time by fixing a sieve for polishing stones of smaller diameter to the lower part of a selecting net above the tube bodies.

CONSTITUTION: When a work is polished, a stone discharge port 10 is opened. Then, a unpolished work thrown in from a throw-in port 22 is lowered through an inside long-sized tube body 3b together with polishing stones, and then elevated through an outside long-sized tube body 3a and passed above the flap and guided to a selecting net 19. The polished work is selected on the selecting net 19, and discharged from the discharge port, and the selected polishing stones are again returned to the inside long-sized tube body 3b. Crushed and worn stones are discharged outside the system during the operation by providing a crushed polishing stone sieve 23. A small-diametered polishing stone receiver 24 is provided outside the sieve, and the grinding stones of small diameter are accumulated in this small-diametered polishing stone receiver 24.