PURPOSE: To improve polishing capacity and workability by arranging a polishing ribbon capable of moving between the guides provided at the tips of a pressurizing and a separating means and an edge surface of a metallic flat wire.

CONSTITUTION: A guide roller 1 supporting one edge surface is arranged on a base T on which a metallic flat line W runs while a polishing ribbon 2 is arranged on the other edge surface in the axial direction. Reels 3,4 are provided on both ends of the polishing ribbon 2 and a lower speed motor 5 is prepared as a mobile means on a reel side 4 to coil the polishing ribbon 2. And, on the side of the polishing ribbon 2 is arranged a micro cylinder 6 having at air piping as a pressurizing means and a pressurizing guide roller 7 having a groove similar to an edge surface shape is set freely rotatably to an axis on the bracket fixed to the tip of the rod 6a of the cylinder. Accordingly, the edge surface of the metallic flat wire W can be pressurized by the polishing ribbon 2 with a fixed force and polished, the abutting surface with the polishing ribbon 2 can be moved, no reduction of polishing capacity and no polishing nonuniformity are generated by clogging and continuous polishing excellent in precision can be performed to the edge surface.