PURPOSE: To obtain a resistance welded tube having an excellent welding characteristic and a good surface by providing a high frequency induction heating device on the upper part of a position converging a joining surface into a V- shape, melting wire-shape metal continuously, refining molten drops in inert gas of a specified flow seed and adding them near the converging position.

CONSTITUTION: In the manufacture of the resistance welded tube, a metallic wire 5 is melted continuously by the high frequency induction heating device 4 provided on the upper part of a position where the facing edges 1, 1' of an open pipe OP are converged in the V-shape. When the welded drops are refined in the inert gas having ≥100m/sec flow speed and added near the converging position, an resistance welded tube P excellent in mechanical properly and good in surface characteristic can be obtained. Further, the same result can be obtained in the manufacture of a spiral steel tube, a shape steel, etc., too, other than the resistance welded tube.