A polybutylene terephthalate resin composition in which it is possible to effectively suppress discoloration without lowering the heat shock resistance. The polybutylene terephthalate resin composition is part of a molded article having a lightness L* value of 80 or higher as measured using a color difference meter, and includes a polybutylene terephthalate resin having a terminal carboxyl group content of 30 meq/kg or less, a carbodiimide compound, and a phosphite compound; and the phosphite compound content is 0.05-0.15 parts by mass per 100 parts by mass of polybutylene terephthalate resin.