PURPOSE: To provide the welding wire for which a plating process of an efficient loop process is adopted and which is decreased in the variation in plating film thickness and is lessened in adhesion of Cu powder.

CONSTITUTION: This welding wire is produced by subjecting the wire to primary drawing down to an intermediate diameter of 3.3mm at Rmax≤25.0μm and Rz≤15.0μm with multistage rolling mills, subjecting the wire to Cu plating in the loop process type plating system and subjecting the wire to secondary drawing down to the final diameter of 1.2mm with multistage type drawing dies. PR control set to spend the time for electrolytic polishing in such a manner that the plating surface roughness of the intermediate-diameter wire satisfies Rmax≤12.5μm and Rz≤7.0μm is executed in the loop process type plating process. The variation in the plating thickness is lessened and the production and adhesion of the Cu powder at the time of the secondary drawing are decreased.