Abstract: A conductor is installed along a Vee-angle part of a tube to be welded for producing an electric welded tube by high frequency resistance or induction welding. The conductor is set closely above the Vee-angle part. A high-frequency current having about the same phase as a phase of a high-frequency current for welding is supplied to the conductor. This controls the distribution of the current density on mating surfaces of Vee-angle part so that the welding current does not concentrate in the upper and lower edges of the tube, thus making uniform the current density and heating in the Vee-angle part.