PURPOSE: To improve the dimensional accuracy and productivity of products by installing tilt rolling mills into tandem and rolling a stock by setting a roll tilt angle of the downstream side mill to be larger than that of the upstream side mill.

CONSTITUTION: Tilt rolling mills 1, 2 are installed into tandem and tilt rolls 10, 20 are tilted by prescribed angles of β1, β2 to the pass line X-X of a tube P, respectively. Further, plugs 11, 21 are arranged so as to align their axial line with the pass-line X-X. At this time, the angle β2 is set to be larger than the angle β1 and the tilt angle of downstream side rolls is set to be sequentially larger than that of upstream side rolls. At the time of rolling a stock with the outside diameter and the number of rotations of the rolls 10, 20 are equal to each other, rolling speeds sequentially increase toward the downstream side, so that rolling with a large stretch ratio is performed. Hence, both the dimensional accuracy and productivity are improved.