A nonaqueous electrolyte secondary battery includes an electrode assembly including a negative plate and a positive plate including a positive electrode active material mix layer, a nonaqueous electrolyte, a battery case that houses the electrode assembly and the nonaqueous electrolyte, and a pressure-sensitive safety system that operates when the pressure in the battery case reaches a value greater than or equal to a predetermined value. The positive electrode active material mix layer contains lithium carbonate and lithium phosphate. The average particle size of lithium carbonate contained in the positive electrode active material mix layer is greater than the average particle size of lithium phosphate contained in the positive electrode active material mix layer. The number of particles of lithium carbonate contained in the positive electrode active material mix layer is less than the number of particles of lithium phosphate contained in the positive electrode active material mix layer.