A polyester film fulfilling formulas (SY150) > (SX150): (I), (SY150) >= 15%: (II), and (SY90) < 15%: (III), when the main orientation axis direction of the film is the X direction, a direction orthogonal to the X direction is the Y direction, the thermal shrinkage at 150 DEG C in the X direction is SX150, the thermal shrinkage at 150 DEG C in the Y direction is SY150, and the thermal shrinkage at90 DEG C in the Y direction is SY90. A polyester film suitable for packaging, decorative, and optical applications, etc., can be provided as a result of the thermal shrinkage being low in a low-temperature area and uniform thermal shrinkage properties being able to be shown in a high-temperature area.