The invention provides a heat-shrinkable polyester film which has a high heat shrinkage rate in the width direction, exhibits a low heat shrinkage rate in the longitudinal direction, and has a great mechanical strength in the longitudinal direction, good openability along perforations, and excellent shrink finish. The film has a hot-water heat shrinkage rate of 40% to 85% in the main shrinking direction and −5% to 15% in the perpendicular direction when the film is immersed in hot water at 98° C. for 10 seconds, and a maximum shrinkage stress of 2-7 MPa in the main shrinking direction when measured in hot air of 90° C. and the shrinkage stress 30 seconds after measurement of the shrinkage stress has started is of 60-100% of the maximum shrinkage stress. The film contains 6 mol % or more of diethylene glycol-derived constituent units with respect to 100 mol % of all polyester resin components.