Disclosed is a resin composition having excellent impact resistance and impact whitening resistance without deteriorating excellent transparency of a methacrylic resin. Specifically, an impact resistance modifier composed of a multilayered polymer having at least three layers, namely an innermost-layer of a polymer containing an alkyl methacrylate, an intermediate-layer of a polymer containing analkyl acrylate, and an outer-layer of a polymer having a Tg of 20-80 1/2 C, wherein the polymer of the intermediate-layer has a mass-average particle size of 200-300 nm and the mass ratio among the three layers is within an appropriate range is blended into a methacrylic resin.