A thermoplastic resin composition of the present invention has high impact resistance, not lowering the weather resistance thereof, even though the amount of an impact resistance improver added thereto is small. The thermoplastic resin composition contains 100 parts by weight of (A) a thermoplastic resin and from 0.5 to 20 parts by weight of (B) a graft copolymer, wherein the graft copolymer (B) contains from 70% to 99% by weight of a crosslinked core (b2) prepared through polymerization of a monomer for the core (b2), containing 70% by weight or more of an acrylate, in the presence of from 0.5% to 20% by weight of a non-crosslinked seed (b1) having a weight-average molecular weight of 40,000 or less, and from 0.5% to 10% by weight of a shell (b3) prepared through polymerization of a monomer for the shell (b3) containing 50% by weight or more of a methacrylate, and the thermoplastic composition further contains from 0.01 to 3.0 parts by weight of (C) a water-soluble polymer compound having the property of forming a physical gel, relative to 100 parts by weight of the graft copolymer (B).