The utility model provides a welding torch, which is used for performing electric arc welding on a second plate (50) and a joint auxiliary component (30) for a plate group formed by embedding or fixing the steel joint auxiliary component (30) on a non-ferrous first plate (40) and overlapping the first plate (40) and the steel second plate (50), and the joint auxiliary component (30) is provided with a step with a shaft part (31) and a flange part, the welding torch is provided with a nozzle (15) which is in contact with the engagement assist member (30) and presses the first plate (40) towardthe second plate (50) via the engagement assist member (30), and the axial end (15e) of the nozzle (15) is provided with a pressing part (15p) which presses the upper surface of the flange part closerto the outer diameter than the upper surface of the flange part, and a protruding part (15d). The axial length of the protruding part (15d) is shorter than the thickness of the flange part.