A polybutylene terephthalate resin composition containing a polybutylene terephthalate resin, 10 to 20% by mass of glass fiber relative to a total mass of the composition, an ethylene/ethyl acrylate copolymer, and an epoxy compound having an epoxy equivalent weight of 600 to 1,500 g/equivalent, and having a comparative tracking index (CTI) of 600 V or higher, measured in accordance with the third edition of IEC 60112.