A method for producing biaxially stretched polyester film comprising Operation A through Operation D, below, wherein Tc refers to crystallization temperature when heated (° C), Tg refers to glass transition temperature (° C), and Tm refers to melting point (° C); Operation A: Operation in which composition comprising polyester resin for which Tc - (Tg + Tm)/2 is not less than -25° C but not greater than 35° C is melt extruded to obtain unstretched polyester resin composition sheet; Operation B: Operation in which the unstretched polyester resin composition sheet obtained at Operation A is heated so as to be within the range not less than Tg + 5 (° C) of the polyester resin but not greater than Tg + 40 (° C) of the polyester resin, and this is stretched so that the stretching ratio in the machine direction is within the range not less than 2x but not greater than 6x to obtain uniaxially oriented polyester resin composition film; Operation C: Operation in which the uniaxially oriented polyester resin composition film obtained at Operation B is heated so as to be within the range not less than Tc - 46 (° C) of the polyester resin but not greater than Tc + 25 (° C) of the polyester resin, and this is stretched so that the stretching ratio in the transverse direction is within the range not less than 4x but not greater than 8x to obtain biaxially oriented polyester resin composition film; Operation D: Operation in which the biaxially oriented polyester resin composition film obtained at Operation C is made to undergo relaxation within the range not less than 3% but not greater than 20% in the transverse direction of the film as it is heated so as to be within the range not less than Tm - 40 (° C) of the polyester resin but not greater than Tm - 5 (° C) of the polyester resin. Operation A: Operation in which composition comprising polyester resin for which Tc - (Tg + Tm)/2 is not less than -25° C but not greater than 35° C is melt extruded to obtain unstretched polyester resin composition sheet; Operation B: Operation in which the unstretched polyester resin composition sheet obtained at Operation A is heated so as to be within the range not less than Tg + 5 (° C) of the polyester resin but not greater than Tg + 40 (° C) of the polyester resin, and this is stretched so that the stretching ratio in the machine direction is within the range not less than 2x but not greater than 6x to obtain uniaxially oriented polyester resin composition film; Operation C: Operation in which the uniaxially oriented polyester resin composition film obtained at Operation B is heated so as to be within the range not less than Tc - 46 (° C) of the polyester resin but not greater than Tc + 25 (° C) of the polyester resin, and this is stretched so that the stretching ratio in the transverse direction is within the range not less than 4x but not greater than 8x to obtain biaxially oriented polyester resin composition film; Operation D: Operation in which the biaxially oriented polyester resin composition film obtained at Operation C is made to undergo relaxation within the range not less than 3% but not greater than 20% in the transverse direction of the film as it is heated so as to be within the range not less than Tm - 40 (° C) of the polyester resin but not greater than Tm - 5 (° C) of the polyester resin.