Heat shrinkable polyester film and package

[Problem] To provide a heat shrinkable polyester film that has sufficient thermal shrinkage characteristics in the main shrinkage direction, which is the longitudinal direction, without containing a large amount of a monomer component that may serve as an amorphous component, while having low thermal shrinkage in the width direction, which is perpendicular to the main shrinkage direction, and low shrinkage stress. [Solution] A heat shrinkable polyester film which contains ethylene terephthalate as a main constituent, while containing from 0 mol% to 5 mol% (inclusive) of a monomer component that may serve as an amorphous component in all polyester resin components, and which is characterized by satisfying the following conditions (1)-(4). (1) The hot water thermal shrinkage in the main shrinkage direction of film is from 15% to 50% (inclusive) in cases where the film is treated in a hot water at 90°C for 10 seconds. (2) The hot water thermal shrinkage in the width direction, which is perpendicular to the main shrinkage direction of film, is from 0% to 12% (inclusive) in cases where the film is treated in a hot water at 90°C for 10 seconds. (3) The maximum shrinkage stress in the main shrinkage direction of film as measured in a hot air at 90°C is from 2 MPa to 10 MPa (inclusive). (4) A constituent unit derived from diethylene glycol is contained in an amount of from 7 mol% to 30 mol% (inclusive) in 100 mol% of all polyester resin components.