To prevent flashes scattering in a pipe in welding from accumulating on an impeder, mandrel, bead grinding bite and a roller.

In a device for manufacturing a resistance welded pipe 2 for which both edges of an open pipe 1 are heated intensively through Joule's heat by high frequency current, pressurized horizontally by a squeeze roll 4, and joined; a vertical through-hole 10 is provided at a position corresponding to the lower part of the edge joining point 9 of the open pipe 1 in a mandrel 7 with an impeder 8 arranged near the axial center, discharging flashes scattering at the joining point 9 of both edges to the lower part of the mandrel 7 by way of the through-hole 10.