PURPOSE: To prevent drop of productivity by countervailing the warp of a pipe stock caused by a residual welding stress and reducing the load on a turks- head, etc., to stably manufacture a straight pipe in a manufacturing method for a welded steel pipe.

CONSTITUTION: By setting the height of a roll throat of a final stand in a fin path provided immediately before a squeeze roll stand 7 higher than the height 11 of a mill path line by ΔH, a bending strain is applied toward the bottom of pipe backing the seam line by three point bending with a fin path roll 5 on the fore stage of a roll 5a and three rolls of the squeeze roll stand 7 and the warp of pipe is reduced by countervailing the warp of pipe stock caused by the residual welding stress.