Provided is a polybutylene terephthalate resin composition which has further improved fluidity (melt fluidity) while maintaining mechanical characteristics. The polybutylene terephthalate resin composition contains 0.05-5 parts by mass of a glycerin fatty acid ester having a hydroxyl value of 200-400, and 0.05-5 parts by mass of a polyvalent alcohol fatty acid ester having a hydroxyl value of 100 or less, with respect to 100 parts by mass of a polybutylene terephthalate resin. The glycerin fatty acid ester preferably contains glycerin and/or a dehydration condensation product thereof, and a fatty acid having 12 or more carbon atoms.