PURPOSE: To uniformize a metallic luster and eliminate of any flatness in a square part by polishing a jaggy mat, where media (abradants) are embedded, after lining the inner part of a polishing container.

CONSTITUTION: A jaggy mat, where media (abradants) 1 are embedded, is lined to the inside of a polishing container 3. With this lining, the media 1 and products both go to relative movements, and the jaggy surface also serves as media, so polishing efficiency is increased so well and, what is more, an uneven surface comes as a catch in rotation of the polishing container 1 and thus the products (for example, coins and medals) become well stirred in consequence. Therefore a uniform gloss is secured on the whole surface of each product in a short time and any flatness in a squre part is eliminated.