A flame retardant resin composition which includes the following component (A) and component (B) blended in the ratio (A):(B)=100:1-40 parts by weight. Component (A) is a thermoplastic resin including 0-70% by weight of a rubber component and 100-30% by weight of a polymer component formed from monomers comprising a methylated aromatic vinyl monomer and an hydroxylated aromatic vinyl monomer and, optionally, an aromatic vinyl monomer other than the above monomers, a cyanated vinyl monomer, a (meth)acrylic acid ester monomer, maleic anhydride, and a maleimide monomer; graft ratio of the thermoplastic resin being 10-150% when the rubber component is used. Component (B) is a flame retarder.