To constitute a device for making a polishing material flow in the axial direction simply, for example, in a polishing device for storing the polishing material and an article to be polished in a polishing tank and polishing the article to be polished by the flow of the polishing material by the rotation of the polishing tank.

The phase of the tops a,... of the polygon on one side of a polishing tank 6 as a hollow vessel with a polygonal section is made different from that of the tops b,... of the polygon on the other side. At the constitution time of a wall surface, its production is facilitated by combining triangle shape plates 12,... with no twisting. Further, when the section shape of the polishing tank 6 is a regular n-sided shape, the shift of the phase of a top is made by 360°/2n.