A biaxially oriented polyester film having the following physical property is provided: when cooled from the molten state at a cooling rate of 20° C./min, an observed recrystallization temperature is 175° C.-200° C. The biaxially oriented polyester film is formed by a thick sheet before bidirectional stretching that is melted and extruded by an extruder and then cooled and formed on a casting roll. The thick sheet before stretching having the following physical property as analyzed by differential scanning calorimetry: a crystallization rate is less than 10%.