A fillet weld joint of steel having high fatigue strength by improving stress concentration without excessively relying on imparting a compressive residual stress to a toe part by welding materials, free of cracking, and excellent in the toughness, and a method for gas shielded arc welding for obtaining the fillet weld joint are provided. In the fillet weld joint, a martensitic transformation starting temperature (Ms point) of a weld metal is 400° C. or above and 550° C. or below, a value obtained by dividing a toe radius ρ of a toe part of welding by a sheet thickness t of a base metal (ρ/t) is 0.25 or above, an expression below Ms(° C.)≦375×[ρ/t]+320  (1) is satisfied, and a crack defect does not exist.