To provide a resin composition containing a phosphorus compound, an aromatic polycarbonate and a rubber-reinforced styrene resin and excellent in flame retardancy, physical properties and processability by adding a phosphazene to a specified resin mixture.

This thermoplastic resin composition is prepared by adding 1-30 pts.wt. phosphazene (D) of formula I or II (wherein (n) is 0-15; and R is an arbitrary functional group such as an alkyl or an acyl) and PTFE (E) to 100 pts.wt. resin mixture prepared by mixing 40-90 pts.wt. bisphenol A type polycarbonate (A) synthesized from bisphenol A and phosgene and having a weight-average molecular weight of 17,000-30,000 with 1-60 pts.wt. graft copolymer (B) prepared by grafting a monomer mixture comprising 60-90wt.% aromatic vinyl monomer and 10-40wt.% monomer copolymerizable therewith onto a rubbery polymer of a glass transition temperature of -20°C or below and 0-40wt.% copolymer (C) prepared by copolymerizing an aromatic vinyl monomer with a monomer copolymerizable therewith.