PURPOSE: To improve the productivity of a steel pipe finishing machine by moving back the steel pipe finishing machine considering the point of time when the detected value of a load current of a motor for rotting a cutting tool coincides with the set value of a no load current as the point of time when clear cutting work has been completed.

CONSTITUTION: When a motor 3 for rotting a cutting tool is operated at a fixed rotating speed to move ahead a steel pipe finishing machine 1, and the cutting tool 2 begins to cut the periphery of the upset portion of a steel pipe P, a load current value detected by a current detector 5 rises quickly from a noload current value I0. A cutting work is carried out at a current value I1 corresponding to a cutting load, and the current value returns to the value I0 the at the moment when the cutting work has been completed. When the load current value detected by the current detector 5 becomes equal to the set value of a noload current, a relative computer control section 6 delivers the completed signal of cutting work to a reversible motor 4 for forward and backward movement. The reversible motor 4 is stopped and inversely rotated by the above signal to move back the steel pipe finishing machine 1 to a waiting position. A net cutting hour measured with timer 7 is read out on a recording indicator 8, and the amount of cutting is recorded and indicated, and the length of the upset portion is also controlled.