PURPOSE: To better the fluidity of the material in a container and to obtain a high polishing efficiency, by providing a container rocking means, which rocks the container so that the material in the container is flowed by drawing a figure eight like locus in the vertical face.

CONSTITUTION: A freely rockable container 10 whose upper part is released and in whose inside the body to be polished is stored together with abrasives, is provided. The container 10 is rocked by a container rocking means 20 so that the material in this container 10 is flowed by drawing a figure 8 like locus inside the vertical face. Consequently, an excellent polishing efficiency can be obtained because the material in the container 10 is flowed by drawing a figure 8 like locus inside the vertical face and all of materials are motioned uniformly and strongly without any dead angle.