A blow-molded foam is provided by foaming and blow-molding the resin material including a polyethylene resin. The foamed resin includes the antioxidant by 300 ppm or more in total. The antioxidant is preferably the combination of a phosphorus antioxidant and a phenolic antioxidant. The optimum amount of phosphorus antioxidant to be included is 250 ppm to 3000 ppm, and that of phenolic antioxidant is 250 ppm to 750 ppm. In the manufacture, the collected resin material and the resin including 300 ppm or more of the antioxidant are melted and kneaded and the foaming agent is mixed thereto to provide the foamed resin, and the foamed resin is blow-molded.