A biaxially extended polyester film which comprises a polyester resin having ethylene A biaxially oriented polyester film comprises a polyester resin having ethylene terephthalate and ethylene isophthalate repeating units in a weight ratio of 90:10 to 75:25; 0.02 to 0.06 weight % of an organic phosphite or phosphate ester; and 0.01 to 0.05 weight % of a hindered phenol compound, wherein the film possesses good thermal stability, processability, and thermal adhesive strength to a metal surface and is useful in forming the inner laminate layer of a metal container.