PURPOSE: To manufacture plural hollow pipes from one billet by cutting a hollow pipe on an outlet side of a piercing mill by a traveling cutting machine into a prescribed length while piercing the billet.

CONSTITUTION: When the piercing is started, bar steadiers 3W7 hold a core bar 9, by properly setting the setting numbers and setting positions of the bar steadiers, any vibration of a plug 2 is not generated even if the length of the core bar 9 is lengthened by two fold. Then, as the piercing is advanced, the bar steadiers are released successively, when the pipe becomes to the prescribed length, it is cut by the traveling cutting machine 10. At a succeeding stage, the cut hollow pipe is sent forward and the bar steadiers 3W5 hold the core bar 9 again. By this method, the plural pipes are obtained from the one billet 11.