The nonaqueous electrolyte secondary battery 100 herein proposed is characterized by being manufactured by performing an initial charging and discharging treatment on an assembly, in which are accommodated in a battery case 80 an electrode body 40, and a nonaqueous electrolyte containing a compound expressed by a general formula: A+[PX6-2n(C2O4)n]−, the content of the compound being 1.1 mass % to 1.2 mass % when the total mass of the nonaqueous electrolyte is assumed to be 100 mass %.