PURPOSE: To efficiently manufacture a titanium seamless tube in a continuous line by piercing and rolling a conjugate billet for which the peripheral surface of a titanium core stock is covered with an iron base metal at a temp. lower than the β transformation point.

CONSTITUTION: A titanium core stock 1 is closely fitted into a cup-shaped iron base metal stock 20. Then, only the stock 20 is reduced its thickness and diameter and is tightly joined to the periphery of the core stock 1 when the stock 1 and 20 are pushed into a die 4 from the bottom side to form a conjugate billet 3. Next, the periphery of the open edge of the stock 20 is totally seal welded to the stock 1 and the billet 3 is heated and is pierced and rolled by a piercing mill provided with cross helical rolls. In that time, a heating temp. is controlled to be lower than the β transformation point of the stock 1.