A non-aqueous electrolyte secondary battery includes a positive electrode containing active material particles composed of a core section formed of olivine type LiFePO4; an intermediate section that lies on the outer side of the core section and has LiFexPyOz; and a surface section that lies on the outer side of the intermediate section and has LiFeaPbOc; and a negative electrode containing lithium titanate, in which battery the molar concentration ratio of Fe relative to P at the core section is greater than the average of x/y of LiFexPyOz, the average value of a/b of LiFeaPbOc at the surface section of the positive electrode active material particles is smaller than the average of x/y of LiFexPyOz, and the positive electrode active material particles include a region in which x/y of LiFexPyOz at the intermediate section increases continuously or intermittently in the direction from the surface section toward the core section.