PURPOSE: To reliably prevent pit flaws by a procedure in which a bored steel piece is roughly rolled into a tube by a mandrel, etc., the unformed portion of the tube end is cut off, and lastly the fin at the cut end portion is removed and finish rolling is made by a stretch reducer, etc..

CONSTITUTION: After removing flaws on the outside surface, the billet 1 is charged into the heating furnace 2 kept it at a definite temperature, then centering and boring is performed by the piercer 3, then rough rolling is made by the mandrel 4 and then the mandrel is drawn out, and lastly the unformed portion of the tube end is cut off by the friction saw 5. Then, the fins B on the inside and outside surfaces of the cut tube 1a are removed by the fin remover 7 such as wire brush, etc., and the tube is charged into the reheating furnace 6. Then, after removing scale by the descaler 8, outside diameter drafting and thick portion processing are made by the stretch reducer 9, and then final processing as is used usually is made to obtain product.