PURPOSE: To provide a polyester resin composition containing a polyester and a graft copolymerization-reactional product of a specific copolymer and a modified polypropylene, containing the polyester and the polypropylene resin in highly compatibilized state and having excellent impact strength, rigidity, etc.

CONSTITUTION: This resin composition is composed of (A) 1-50wt.% of a graft- copolymerization reactional product produced by melting and kneading (i) 5-95wt.% of a copolymer of ethylene, an unsaturated glycidyl compound (preferably glycidyl methacrylate) and an acrylate monomer (preferably methyl acrylate) with (ii) 95-5wt.% of a polypropylene modified with an unsaturated carboxylic acid (anhydride) and (B) 50-99wt.% of a polyester (preferably polybutylene terephthalate). The component A is produced preferably by kneading the components (i) and (ii) with a kneader such as twin-screw extruder in molten state at 230-280°C. The unsaturated carboxylic acid (anhydride) is preferably a dicarboxylic acid (anhydride) such as maleic acid.