It is an object of the present invention to provide a polybutylene terephthalate resin composition, excellent in toughness, in hydrolysis proofing and moreover in chemical proofing. Specifically, there are blended (A) 100 parts by weight of a polybutylene terephthalate resin, (B) 20 to 40 parts by weight of an acrylic core-shell polymer in which a butadiene component is not contained, (C) 0.1 to 5 parts by weight of an epoxy compound, and (D) 0.05 to 1 parts by weight of an aromatic carbodiimide compound.