An outer casing for an electric device which is a molded article of a environmental resin wherein poly(lactic acid) and/or a lactic acid copolymer is used, is constituted by molding a flame-retarded resin composition including a resin component containing poly(lactic acid) and/or the lactic acid copolymer as a main ingredient, and silica-magnesia catalyst particles as a flame retardance-imparting component which imparts flame retardance, wherein an organometallic compound is attached to a part of surfaces or the entire surfaces of the silica-magnesia catalyst particles. The organometallic compound is preferably a titanium-based coupling agent or a zirconium-based coupling agent.