To provide a biaxially oriented polyester film which is obtained by a simultaneous biaxial orientation system, has a sufficient thickness to control deformation due to self weight of the film, superior transparency, and transparency uniform in the width direction of the film.

The biaxially oriented polyester film is made of a polyester composition obtained by melt-kneading 10-90 pts.mass of a polyester (A) based on repeating units of ethylene terephthalate with 90-10 pts.mass of a polyester (B) based on repeating units of ethylene terephthalate having an intrinsic viscosity at least 0.05 dl/g higher than that of the polyester (A), is oriented by a simultaneous biaxial orientation system, and has a thickness of ≥100 μm. The half-crystallization time of the polyester composition at 170°C is 30 s or longer.