PURPOSE: To restraint vibration of a rolling plug and to reduce wall deviations of a pipe stock by obtaining a reeling part length of the rolling plug rear end by an equation and rolling a pipe by adjusting an outlet side face angle of rolling rolls to a tilting angle of the reeling part.

CONSTITUTION: A reeling part length (l) of a rolling plug 7 is shown by an equation of (l)≥πDbsinβ/2 because a pipe stock 3a is subjected to one rolling by rolling rolls 1, 2 while the stock 3a rotates one rotation. In the equation, Db shows a pipe stock outer diameter, β shows a roll feed angle. The reeling part of the plug 7 should be straightened as much as possible, considering for a correlation between the reeling part and rolling face of the rolls 1, 2. Therefore, an outside face angle α2 of the rolls 1, 2 is adjusted so that the reeling part parallels to the outlet side face of the rolls 1, 2 at the contact point with the stock 3a. A truncated chevron angle γ of the rolls 1, 2 are independently adjusted to perform piercing and rolling as that means.