Disclosed is a nonaqueous electrolyte secondary battery which comprises a flat wound electrode body wherein a positive electrode plate, which comprises a positive electrode collector foil and a positive electrode active material layer, and a negative electrode plate, which comprises a negative electrode collector foil and a negative electrode active material layer, are wound up with a separator being interposed therebetween. The positive electrode plate has a collector cover layer that has electrical insulation properties and covers at least a part of a facing collector portion in the longitudinal direction in a positive electrode collector portion. The collector cover layer covers at least an innermost semi-cylindrical facing collector portion which forms the innermost part of the facing collector portion and has a half-cylindrical shape.