A resin composition comprising a 2-(1-arylalkylidene) acetic ester and at least one resin selected from a methyl methacrylate resin, a styrene resin and a methyl methacrylate-styrene copolymer resin is provided, wherein the acetic ester is contained in the composition in an amount of from about 0.0005 part by weight to about 0.1 part by weight with respect to 100 parts by weight of the resin. The resin composition is improved in durability without deteriorating the excellent properties of the resin, such as being colorless and transparent.