PURPOSE: To enhance the efficiency of polishing, by securing, to the inner surface of a treating tank, spiral depressing blades for depressing materials to be polished in the direction of the rotating axis so that the stirring of the materials to be polished and a polishing agent is promoted.

CONSTITUTION: Depressing blades 10 having a spiral form leading in the direction of a rotary shaft 8, for stirring and depressing downward materials 12 to be polished, is secured in a treating tank 6. The polishing is carried out by operating a drive motor 18 after a compound 14 and the materials 12 to be polished are taken into a tank 6 in a stirring type polishing machine 2 through a hopper 16. The materials 12 to be polished and the compound 14 reach the bottom 6b of the tank 6 by being depressed by the depressing blades 10, and are again displaced in the direction of B after they are once raised (R) from the bottom 6b by being jostled together. Meanwhile, the polishing due to the stirring is effectively made.