PURPOSE: To sharply reduce the occurrence of a trouble, such as breakage of the side plate of a polishing tank, by locating a polishing tank support rotary shaft along the direction of length in a manner to extend through the polishing tank.

CONSTITUTION: A polishing tank support rotary shaft 3 is extended through the central part of a polishing tank 4 or along the direction of the length of the polishing tank. Thereby, abundant load resistance is provided and a further more quantities of polishing materials and works can be contained. When the polishing tank support rotary shaft 3 is extended directly through a turret drum, a single or a plurality of the polishing tanks having various sizes are mounted to the periphery or the surroundings of the polishing tank support rotary shaft 3 and can be rotated, resulting in improvement of productivity and economical efficiency.