PURPOSE: To prevent the wall-thickness deviation of a metallic pipe by rolling again a part, rolled by a roll of one side and a reeling part of plug, by a roll of the other side and the reeling part of plug, in piercing the pipe by skew rolls.

CONSTITUTION: With respect to a plug 2 used for skew rolling, the length LR of a reeling part 22 in the axial direction of plug 2 is decided by the relation between the outer diameter DS of a stock B after rolling and the slant angle βof skew rolls 1(l), 1(r). In case of piercing the stock B; the rolled part, rolled by the roll 1(l) of one side and the part 22, is rolled again by the other roll 1(r) and the part 22. In this way, a metallic pipe having uniform wall thickness is obtained regardless of its circumferential position.