PURPOSE: To obtain a high-gloss, weather-resistant resin compsn., by grafting an arom. vinyl monomer and a vinyl cyanide monomer, etc., onto a rubber mainly composed of an alkyl acrylate.

CONSTITUTION: A compsn. is formed from 10W100wt% graft polymer (A) and 0W90wt% copolymer (B). (A): a graft copolymer obtd. by polymerizing 20W900 pts.wt. grafting monomer mixture of 40W90wt% arom. vinyl monomer, 0W40wt% vinyl cyanide monomer and 0W40wt% copolymerizable vinyl monomer in the presence of 0.01W5pts.wt. (per 100pts.wt. monomer mixture) polymn. initiator of formula II or III onto 100pts.wt. rubbery polymer composed of 60W99.99wt% 1W12C alkyl acrylate, 0W40wt% vinyl or vinylidene monomer copolymerizable therewith and 0.01W20wt% crosslinking compd. having at least two unsaturated bonds of formula I. (B): a copolymer composed of a monomer mixture having the same composition as that of said grafting monomer mixture.