A heat-shrinkable polyester film is provided which exhibits a high shrinkability in a high-temperature range with a main shrinking direction oriented in a longitudinal direction thereof, though not shrinking in the longitudinal direction in a low-temperature range, possesses an extremely high mechanical strength in a transverse direction orthogonal to the main shrinking direction, and, in particular, can be utilized suitably as a film for forming a jacket label of a battery or in similar applications.