PURPOSE: To efficiently perform the bevel machining on the outer periphery of various steel pipes, e.g., a rectangular steel pipe, a round steel pipe, by employing a profile cutting method using the inner periphery as a reference.

CONSTITUTION: A rotary cutter 40 is rotated on the outer periphery of a work W and also an extension means is operated so that a cutting mechanism is brought near to the work W. A copying roller 43 gets into contact with the inner periphery of the work W, and the rotary cutter 40 adjacent to this copying roller 43 cuts into the outer periphery of the work W. A bevel section with a root face R and a bevel angle θ is cut out on this outer periphery. The standard at this time is determined from a conversion table using the thickness of the material, bevel angle, and root face as data.