A submerged arc welding process using welding wire containing, based on the total mass of the welding wire, Ni: 50% or more by mass, Cr: 14.5% to 16.5% by mass, Mo: 15.0% to 17.0% by mass, W: 3.0% to 4.5% by mass, Fe: 4.0% to 7.0% by mass, and C, Si, Mn, P, S, Cu, V, Co, and Al: a predetermined amount or less, and a bonded flux containing, based on the total mass of the bonded flux, Al2O3: 35% to 55% by mass, SiO2: 5% to 25% by mass, CaO: 2% to 10% by mass, CaF2: 25% to 45% by mass, and Na2O: 2% to 4% by mass.