PURPOSE: To provide the titled resin composition having improved impact resistance, by blending a rigid methacrylic copolymer with a multi-stage polymerization resin composition produced by the suspension polymerization process properly combining the polymerization conditions, the composition of the monomer mixture and the timing of the addition of various monomers.

CONSTITUTION: The objective composition is produced by compounding (A) 5W95wt% rigid methacrylic resin composition obtained by the polymerization of a monomer mixture composed mainly of an alkyl methacrylate with (B) 95W 5wt% multi-stage polymerization resin composition obtained by the multi-stage polymerization process comprising (i) the first stage consisting of the suspension polymerization of a monomer fixture composed mainly of methyl methacrylate to form a rigid resin layer, (ii) the second stage comprising the addition of a monomer mixture composed mainly of an acrylic acid ester to the polymerization system after the temperature of the system begins to increase by the heat of polymerization and before 15min after the peak of the generation of the polymerization heat, and the polymerization of the mixture, and (iii) the third stage comprising the addition and polymerization of a monomer composed mainly of an acrylic acid ester and containing a crosslinking agent.