There are provided a polyethylene terephthalate resin composition in which to 100 parts by weight of a polyethylene terephthalate resin (A) polymerized by use of a germanium catalyst and having at least 80% of an ethylene terephthalate repetition unit, 0.05 to 30 parts by weight of a compound selected from the group consisting of an epoxy compound having at least two intramolecular epoxy groups without any intramolecular ester linkage and a carbodiimide compound (B) is formulated, and resin compositions in which a fibrous reinforcing material (C), a block copolymer (D) and an inorganic nucleating agent (E) are further formulated in the above mentioned composition. The resin composition of the present invention is excellent in moist heat resistance, fluidity and mechanical strength, and in addition, can be subjected to high cycle molding even in a mold of a low temperature to yield a molded article with improved surface characteristics.