A polybutylene terephthalate resin composition which is free from bleeding and other problems, and improves the flowability (melt-flowability) while maintaining the characteristics such as mechanical strength or toughness. To 100 parts by weight of a composition composed of 50 to 90% by weight of (A) a polybutylene terephthalate resin and 10 to 50% by weight of (B) inorganic filler, is blended 0.05 to 5 parts by weight of (C) a glycerin fatty acid ester being composed of glycerin and/or a dehydrated condensate thereof and a fatty acid having 12 or more carbon atoms and having 200 or more hydroxyl value determined by a method specified in the description.