To prevent a polishing failure caused by the failed straightness, failed circularity, polishing thermal distortion, bending or the like of a metallic pipe by providing a means for adjusting the pressing force of a polishing tool in the direction of both horizontal side faces of the metallic pipe, and a means for rotating the metallic pipe by a specified angle in a divided manner with a pipe axis set as a rotary axis.

For polishing a traveling steel pipe, both polishing tools 4 and 4 are rotated, and a truck 2 on a rail 9 is traveled in the pipe axial direction of the steel pipe at a constant speed. For adjusting a polishing amount, the rotary motor load currents of flap wheels 4 and 4 are detected by a meter relay, and a load adjusting motor is controlled. The steel pipe is rotated in a divided manner by a metallic pipe rotating motor 7 at constant angles. After the completion of one-way traveling polishing by both polishing tools 4 and 4, the steel pipe is rotated by an amount equivalent to the polishing width of one time. Reciprocating traveling polishing is repeated, a rotational angle and a rotational speed are set in a controller by the metallic pipe rotating motor 7 so as to polish the full peripheral surface of the steel pipe, and polishing is performed fully automatically.