PURPOSE: To improve the external appearance of the weld zone of after welding by forming the two layer structure composing center and outer layer parts at specified ratio to the whole wire sectional area of a steel wire and increasing the oxygen contg. amt. of the center part more than that of the outer layer part.

CONSTITUTION: The steel wire whose total oxygen amt. is 60W230ppm is made in the two layer structure composing the center part 2 of this wire at 10W60, of the total wire sectional area. Of the two layer structure thus formed the oxygen density of the center part 2 is taken at 100W750ppm and the center part oxygen density/outer layer part oxygen density at ≥1.2. An arc is stabilized and the generation of a spatter is reduced by executing welding by using the wire thus composed.