Disclosed is a resin composition comprising (A) 100 parts by weight of a base resin comprising a rubber-modified styrene-containing graft copolymer and a styrene-containing copolymer; (B) 0.5-8 parts by weight of an acrylic rubber graft copolymer resin having an average particle size of 0.1-0.5 .mu.m; and (C) 0.5-8 parts by weight of a graft copolymer resin comprising an ethylene .alpha.-olefinic copolymer rubber having an average particle size of 0.1-0.8 .mu.m. The thermoplastic resin composition of the present invention greatly improves chemical resistance to insulating materials, such as urethane foam, or foaming agent compounds, such as freon (CFC-11, HCFC-141b, HFC-245fa, HFC-245eb, HFC-245ca, HFC-356mffm) and cyclopentane and offers superior impact strength, whiteness and processability. It can be useful for extrusion sheets of refrigerator interiors.