PURPOSE: To easily and promptly perform automatic separation of a work without causing a flaw, by polishing the work in media circulatively moved in a barrel tank and removably placing a screen, only for the media passable, in the barrel tank.

CONSTITUTION: The lower side of a rotary bottom part 22 in a barrel tank 24 is connected to a motor 18 through a rotary shaft 36, belt 48, etc. A catcher net 79 of screen, collecting a work 76 mixed in the tank 24 from media 78, is mounted to the end part of a vertical portion 74 of a supporting member 68. The net 79 is for catching the work, circulatively moved from the center portion of the tank 24 to its peripheral part side, and provided with plural bar shaped parts, 80, 82 for forming an opening. The circulatively moving media 78 and the work 76 are once introduced to the inside of said net 79, and the introduced media 78 pass through a main screen part 86 of the net 79 to the rear, while the work 76 is blocked its circulation and separated.