To obtain a polyester film having a high gloss value, easily produced at a low production cost and capable of being reused by mixing its regenerated raw material.

This polyester film having preferably ≥70% whiteness, ≥55% opacity (ASTM-D 1003-77) and ≥50% gloss value is obtained by constituting it of a white biaxially stretched polyester film consisting of at least one layer and having at least one base layer consisting of a polyester and 2-60 wt.% cycloolefin copolymer based on the weight of the base layer, having 70-270°C, preferably 90-250°C and more preferably 110-250°C glass transition point. As the cycloolefin copolymer, a copolymer having a polynorbornene, polydimethyloctahydronaphthalene, polycyclopentene or poly(5-methyl)norbornene unit is preferable.