PURPOSE: To stably perform buffing, by interlocking a buff to a change of the center line of a metal rod, controlling the center line of the buff and oscillating the buff.

CONSTITUTION: A hollow buff shaft 4 is inserted between a buff driving side bearing 8 and buff operating side bearing 9, and a buff 1 is pressed to a metal rod 3. A bearing 7 is provided externally of the bearing 8, and the bearing 7 is connected to a driving part of oscillation and centering by a connecting shaft 11, then a buff driving shaft 6 is moved in an axial direction of the buff 1. A sliding pin 10 is mounted to the bearing 8 in a slidable state to the bearing 7 to prevent the bearing 7 from rotating. In case of zigzag motion, centering movement is added to oscillation movement of the buff, and the buff driving shaft is moved in the axial direction of the buff.