To provide the filler metal for oxide diffusion reinforcement type alloy welding by containing C, Si, Mn, Cr, Mo, Fe, Ti, Al, Nb, Co, P, S, Cu and Ni of the prescribed quantity.

The alloy has the composition consisting of, by weight, 0.001-0.15% C, ≤1.0% Si, ≤3.5% Mn, 18.0-50% Cr, ≤10.0 Mo, ≤3.0% Fe, ≤0.8% Ti, ≤1.50% Al, ≤3.0% Nb, ≤15.0% Co, and the balance substantially Ni, and in addition, preferably ≤0.03% P, ≤0.015S, and ≤0.50 Cu. To secure the heat resistance, corrosion resistance and toughness, Ni is contained as the basis, and to secure the oxidation resistance, large volume of Cr is added, and various kinds of solid solution reinforcement element are added to secure the strength. The filler metal is suitable for the MIG welding, TIG welding and plasma welding. When the oxide diffusion reinforcement type alloy is welded using the filler metal, the part of relatively low temperature or of relatively low stress has the strength and ductility sufficient for practical use.