PURPOSE: To obtain the titled resin having remarkably improved change in transparency and chage of flexibility with time and improved processability, by grafting vinyl chloride monomer onto a specific lactone polyester.

CONSTITUTION: (B) Vinyl chloride monomer is grafted onto (A) a lactone polyester having constituent units of the formula (R1 is H or methyl; n is an integer 3W5) and 5,000W200,000 number-average molecular weight, preferably poly(- caprolactone), to give the aimed resin. The content of the component (A) in the above-mentioned resin is preferably 30W70wt%. The graft polymerization is preferably carried out by the suspension polymerization method.