PURPOSE: To perform the continuous production of a striped spiral pipe by forming the step reinforcing edge equivalent to a plate thickness by a driving roll at one side end of a strip sheet, by forming a spiral pipe with lapping the reinforcing edge and the other end of the plate width by a forming roll and by welding with deciding the outer diameter dimension by a fixed form.

CONSTITUTION: A step reinforcing edge 2 equivalent to a plate thickness is formed by a driving roll 4 at one side end of a strip sheet 1. A spiral pipe 7 is then formed with lapping the reinforcing edge 2 and the other end 3 of a plate width by a forming roll 5 and after deciding the outer diameter dimension with a fixed form 6 the lapping parts 2, 3 are welded successively. A striped spiral pipe 7 is produced by welding continuously in good conditions.