PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition with a greatly reduced amount of an out gas generated from a molded article and a molded article using the same.SOLUTION: The thermoplastic polyester resin composition includes 100 mass parts of a thermoplastic polyester resin (A) having a number of OH terminals of 5 to 30 eq/ton and a reduced viscosity of 0.80 to 1.25 dl/g, and 0.01 to 0.20 mass parts of phenyl phosphonic acid (B). A total amount of an out gas generated, when a piece of a flat plate obtained by injection molding the thermoplastic polyester resin composition is heat-treated at 160°C for 15 minutes, is 10 ppm or less. And Charpy impact strength of a test piece obtained by injection molding the thermoplastic polyester resin composition at 250°C with residence time of 10 minutes retains 90% or more of the Charpy impact strength of a test piece obtained by injection molding the thermoplastic polyester resin composition at 250°C with residence time of 0 minutes.
