PURPOSE: To sufficiently polish the material to be polished and to obtain a product of good quality, by performing a barrel polishing with the material to be polished being held inside a holding jig made by providing a window hole on a resin made hollow body having flexibility.

CONSTITUTION: A material to be polished (e.g. coin) 6 is held inside the window hole 2 of a holding jig 5 made by providing the window hole 2 on a thin wall resin made hollow body 1 having flexibility. A barrel polishing is then performed with this jig 5 being put into the mixture of the polishing stone and polishing liquid inside a container 8. The material to be polished is thus subjected to polishing enough because of the polishing stone and polishing liquid being circulated into the holding jig from the window hole, the mutual materials to be polished are not abutted by being protected with the holding jig. So they are not marred.