A thermo-shrinkable polyester film of this invention is obtained from a composition that comprises acid components including terephthalic acid and glycol components including ethyleneglycol. The polyester film has a heat-shrinkage ratio of 30% or more in a certain direction at 100.degree. C., and a shrinkage ratio of 5% or more at the point of intersection of a curve showing the internal shrinkage stress of the film and a curve showing the tensile stress of the film.