PURPOSE: To provide a highly dazzling gloss to metallic materials to be worked by polishing them by the addition of bamboo powder when they are polished by the barrel polishing method.

CONSTITUTION: Metallic materials to be worked such as iron, aluminum, zinc, copper, stainless steel, etc., an abrasive consisting of balls and chips made of iron, magnetic glass, synthetic resins, etc., and a compound consisting of water, about 0.2W5wt.% of a surface active agent to the water are thrown into a polishing vessel of a barrel polishing machine, and more than 0.05wt.%, preferably about 0.1W5wt.% of bamboo powder is added, and then the barrel polishing operation is performed. For the bamboo powder, the powder made of epidermis of a green bamboo is desirable, and the powder must pass through 20 mesh (Tyler mesh), preferably 48 mesh. Thus, the metallic materials can obtain a highly dazzling gloss.