NOVELTY - Manufacturing a biaxially stretched thermoplastic resin film, comprises: performing melt extrusion of a thermoplastic resin into a sheet form and cooling the resultant sheet on a casting drum to form a thermoplastic resin sheet; longitudinally stretching the thermoplastic resin sheet, which is formed, in a longitudinal direction or a rolling direction of the casting drum; and gripping the thermoplastic resin sheet after the longitudinal stretching by a gripping member and transversely stretching the thermoplastic resin sheet in a transverse direction orthogonal to the longitudinal direction.    USE - The method is useful for manufacturing a biaxially stretched thermoplastic resin film, a back sheet for a solar cell and a solar cell module (claimed).    ADVANTAGE - The method provides biaxially stretched thermoplastic resin film with excellent dimensional stability, hydrolysis resistance and durability performance over long time. The solar cell module exhibits satisfactory power generation performance over long time.    DETAILED DESCRIPTION - Manufacturing a biaxially stretched thermoplastic resin film, comprises: performing melt extrusion of a thermoplastic resin into a sheet form and cooling the resultant sheet on a casting drum to form a thermoplastic resin sheet; longitudinally stretching the thermoplastic resin sheet, which is formed, in a longitudinal direction or a rolling direction of the casting drum; and gripping the thermoplastic resin sheet after the longitudinal stretching by a gripping member and transversely stretching the thermoplastic resin sheet in a transverse direction orthogonal to the longitudinal direction, where the transverse stretching includes preheating the thermoplastic resin sheet after the longitudinal stretching to a stretchable temperature, applying a tension to the thermoplastic resin sheet, which is preheated, in the transverse direction orthogonal to the longitudinal direction to transversely stretch the thermoplastic resin sheet, heating the thermoplastic resin film that is obtained by the longitudinal stretching and the transverse stretching to crystallize and thermally fix the thermoplastic resin film, relaxing the tension applied to the thermoplastic resin film that is thermally fixed to remove remaining strain and cooling the thermoplastic resin film after the relaxing of the tension, where at least one of the thermal fixing and thermal relaxing performs contraction treatment of the thermoplastic resin film in the longitudinal direction of the film in such a manner that a contraction ratio expressed by the formula ((((A+B)-(C+B))/(A+B))x 100) is 3-8% while narrowing a grip distance between gripping members adjacent to each other, a total contraction treatment time in the thermal fixing and the thermal relaxing is 10-60 seconds, and an average rising rate of a film surface temperature from a termination point of time of the transverse stretching in the stretching of the film until a film surface temperature reaches a maximum arrival temperature in an interval in which the contraction treatment is performed so as to satisfy the contraction ratio is set to a 0.6-4.5 degrees C/second, where A is grip distance (mm) before narrowing the distance between the gripping members adjacent to each other, B is length (mm) of each of the gripping members in the longitudinal direction of the film and C is grip distance (mm) after narrowing the distance between the gripping members adjacent to each other. INDEPENDENT CLAIMS are included for:    (1) a biaxially stretched thermoplastic resin film that is manufactured by the method, where a thermal contraction ratio, when subjected to the heating in treatment conditions of 150 degrees C and 30 minutes is 2% or less;    (2) a back sheet for a solar cell, comprising the biaxially stretched thermoplastic resin film; and    (3) a solar cell module, comprising a transparent substrate to which solar light is incident, a solar cell element that is disposed on one side of the substrate and the back sheet for a solar cell, that is disposed at a side of the substrate, which is opposite to the side at which the solar cell element is disposed.