The present invention provides a polybutylene terephthalate resin composition which satisfies performances such as high durability in an environment of heating and cooling cycles and adhesion properties to an addition-reaction type silicone rubber. Specifically, provided is the polybutylene terephthalate resin composition, exhibiting excellent adhesion properties to the addition-reaction type silicone rubber, including: (A) 100 parts by weight of polybutylene terephthalate resin; (B) 5 to 30 parts by weight of a styrene-based thermoplastic elastomer containing 40% by weight or less of styrene component; and (C) 20 to 100 parts by weight of glass fiber.