A flame retardant resin composition including the following components (A), (B) and (C) in the ratio (A):(B):(C)=15-99:0-84:1-30% by weight; and wherein the molar ratio of bromine atom and antimony atom is 1.2-4.5:1. Component (A) is a rubber reinforced resin composition including 10-100% by weight of graft copolymer (A-1) which is obtained by the polymerization of (b) 90-30% by weight of monomer components including 5-50% by weight of bromostyrene and 95-50% by weight of one or more monomers selected from the group consisting of aromatic vinyl monomers, cyanated vinyl monomers, (meth)acrylic acid ester monomers, maleic anhydride, and maleimide monomers in the presence of (a) 10-70% by weight of a rubber-like polymer [(a)+(b)=100% by weight] and 90-0% by weight of copolymer (A-2) obtained by the polymerization of 60-90% by weight of aromatic vinyl monomers and 40-10% by weight of one or more monomers selected from the group consisting of cyanated vinyl monomers, (meth)acrylic acid ester monomers, maleic anhydride, and maleimide monomers. Component B is a bromine-containing copolymer obtained by the polymerization of 5-50% by weight of bromostyrene and 95-50% by weight of one or more monomers selected from the group consisting of aromatic vinyl monomers, cyanated vinyl monomers, (meth)acrylic acid ester monomers, maleic anhydride, and maleimide monomers. Component (C) is an antimony oxide.