The invention provides a white polyester film formed with a polyester resin whose main constituent is ethylene terephthalate, and (1) the film has at least two or more layers, and has at least one white layer and at least one heat sealing layer, wherein at least one of the film surfaces is the heat sealing layer, and the film satisfies the prescribed requirements of (2) the peeling strength of the heat sealing layers, (3) the difference in reversing heat capacity between at a lower and a higher temperature than a glass transition temperature of the heat sealing layer, (4) the heat shrinkage in both a longitudinal and width direction when treated in hot water at 80?C. for 10 seconds, (5) the total light transmittance, and (6) the apparent specific gravity.