PURPOSE: To simplify the structure of a device and stably polish a metal wire by forming a container filled with polishing powder into a conical shape or a pyramidal shape, vertically arranging powder into a large diameter set above, and providing metal wire insertion openings at an upper section and a lower section respectively.

CONSTITUTION: A conical or pyramidal container 3 is vertically arranged with the tip section 6 of the small diameter set below, and polishing powder 2 is filled in it. A metal wire 1 is inserted and traveled in the upper opening 4 and lower opening 5 of the container 3. A lower opening 5 is formed to further squeeze the tip section 6 of the small diameter of the container 3, and it is made more slender toward the tip. Only the tip section 6 may be separately formed and fitted. The polishing powder 2, e.g. emery powder, is filled. When the metal wire 1 is vertically traveled, the polishing powder 2 is properly filled at the tip section 6 by the gravitational action and the friction action with the metal wire 1, the friction force of the tip section 6 is inreased, and the metal wire 1 is polished with no reduction of the polishing capability.