Provided is a polybutylene terephthalate resin composition having excellent mold releasability, measurement stability and hydrolysis resistance, and exhibiting minimal discoloration under high-temperature conditions. The polybutylene terephthalate resin composition contains: (A) a polybutylene terephthalate resin, (B) a higher fatty acid ester of pentaerythritol, and (C) a low-molecular weight polyethylene having a number-average molecular weight of 3,000 to 7,000. It is preferable that the component (B) is pentaerythritol tetrastearate, and that the component (C) is a low-molecular weight polyethylene having a number-average molecular weight of 4,500 to 5,500.