An objective of the present invention is to provide an inexpensive and excellent polyester resin sheet for photovoltaic batteries which enhances the electrical transduction efficiency of photovoltaic battery by improving the hydrolysis resistance and heat resistance, and further enhancing the screening potency, as well as a photovoltaic battery using the same. The polyester resin sheet for photovoltaic batteries comprises a polyester resin layer formed by using one or more layers having a number average molecular weight of 18500 to 40000 in which at least one or more layers having 5 to 40% by weight of titanium dioxide is formed on the polyester resin layer, wherein a light transmittance at wavelengths of 300 to 350 nm is 0.005 to 10%, a relative reflectance is 80% or more and 105% or less, an apparent density is 1.37 to 1.65 g/cm3, an optical density is 0.55 to 3.50, and the variation in optical density has a fluctuation of within 20% from the center value.