The present invention relates to a heat-resistant resin composition including a first copolymer including a conjugated diene-based polymer, units derived from an aromatic vinyl-based monomer, and units derived from a vinyl cyan-based monomer; a second copolymer including units derived from an aromatic vinyl-based monomer and units derived from a vinyl cyan-based monomer and having a glass transition temperature of 115° C. or more; and a third copolymer including units derived from an aromatic vinyl-based monomer and units derived from a vinyl cyan-based monomer, wherein the second copolymer has a linear shape, and the third copolymer has a branched shape and a branched degree of 2 to 8.