Disclosed herein are a novel graft copolymer comprising a stock copolymer (A) of at least one monomer selected from esters of unsaturated carboxylic acids and vinyl esters (a), ethylene (b) and carbon monoxide (c), and a polyamide oligomer having a primary amino group at one end of its molecule (B) grafted on said stock copolymer, and a process for the preparation thereof. The proposed graft copolymer, when used as an adhesive, in particular for adhesion of polyvinyl chloride, exhibits excellent heat resistance and adhesion properties.