TECHNOLOGY FOCUS - POLYMERS - Preferred Process: Manufacture of white polyester film involves performing drying process which provides surface inside easily bonding layer with temperature difference of 0.5-10 degrees C, and drying the obtained product to form easily bonding layer, and extending process which provides surface inside polyester film with temperature difference of 0.5-10 degrees C, and in which polyester film is stretched in which easily bonding layer is formed. Manufacture of solar cell module involves heat-processing bonding structure for 1-10 minutes using heater with temperature distribution of 0.5-8 degrees C, and in which before bonding process, the mean-temperature of ethylene-vinyl acetate resin is 40-70 degrees C. Manufacture of white polyester film involves providing temperature difference of 0.1-10 degrees C between surfaces of the polyester film, and cooling the polyester film which has the dried easily bonding layer after the drying process. The resin material in which microparticles are dispersed are injected to melt extruder, and forming layer (L1) in which the dispersion degree of microparticles is 10-100%, with respect to total mass of microparticles, and in which the fluctuation to torque of screw of melt extruder is 0.5-20%. The layer (L1) is formed into film by melt-extruding the melt-kneaded molted resin from die by melt extruder, with temperature variation of 0.5-10 degrees C. Manufacture of white polyester film involves longitudinally stretching the non-expanded polyester film, laterally stretching the polyester film which is longitudinally stretched, and cooling the polyester film after longitudinal stretch between longitudinally stretch process and laterally stretch process with cooling rate of 5-100 degrees C/second. Preferred Properties: The easily bonding layer has surface haze of 0.01-3% and in-plane distribution of surface haze of 0.1-30%. The total thickness of polyester film is 40-350 mu m. The layer (L1) has thickness of 5-80 mu m, and thickness distribution of 1-20%. The white polyester film has breaking elongation reduction-by-half time at the time of exposing at 120 degrees C and humidity of 100 %RH environmental condition, is 70-200. Preferred Composition: The dispersion degree of microparticles in layer (L1) and/or (L2) of polyester film is 10-100%, and the content of polyester including microparticles is 0.06-10 %mass. The white polyester film comprises structure containing polyester film including microparticles and laminated structure of layer (L1) and layer (L2), and easily bonding layer laminated on surface of layer (L1) and layer (L2).