PURPOSE: To prepare the titled composition having high processability and transparency and excellent shape-retainability at high temperature, by mixing a vinyl chloride resin with a polymer obtained by polymerizing a styrene monomer and an alkyl (meth)acrylate in the presence of methylmethacrylate polymer.

CONSTITUTION: The objective composition is prepared by compounding (A) 99W 30pts.wt., preferably 95W50pts.wt. of polyvinyl chloride or a vinyl chloride copolymer having a vinyl chloride content of ≥80wt% with (B) 1W70pts.wt., preferably 5W50pts.wt. of a polymer obtained by polymerizing (i) 1W30wt% monomer mixture consisting of 40W80wt% styrene monomer and 60W20wt% alkyl (meth) acrylate wherein the C number of the alkyl group is 2W18, in the presence of (ii) 99W70wt% methyl methacrylate homopolymer or a copolymer containing ≤25wt% styrene monomer and having a specific viscosity of ≤0.6, preferably ≤0.3 (C=0.4g/100ml benzene, 30°C).