PURPOSE: To shorten working hours in such a way that after completing polish, a tap which closes the bottom of the barrel is pulled up, without mounting and dismounting any cap, content in the barrel is drained, flushing is simply and rapidly done, and re-tapping is done.

CONSTITUTION: After completing polish, a drive axle 2 is decelerated, by which one side of barrels 5, 5 in revolution and rotation is stopped at the fixed position. Subsequently, air is sent into an air pressure cylinder 9, a lever 10 is sent down, a clamp 11 at one end is brought to be engaged with a rod 7 of a tap 6 which closes the bottom part of the barrel 5. With this condition, the air pressure cylinder 9 is conversely worked, the lever 10 is sent up resistingly to repulsive force of said rod 7, the tap 6 is pulled up from the bottom part of the barrel 5, the content after completing polish in the barrel 5 is drained. Then, flush is done in the barrel 5 which has been emptied, after that the tap is re-closed, which is sent to the fixed position where is 180th degree away, and new work piece and polishing material is put into the barrel 5.