A nonaqueous electrolyte secondary battery includes an electrode group prepared by winding spirally or in a flattened shape a laminate structure including a separator interposed between positive and negative electrodes, and a nonaqueous electrolyte held by the electrode group, wherein an edge portion of the separator in a direction perpendicular to a winding direction protrudes outward from edges of the positive and negative electrodes in the direction perpendicular to the winding direction, and the separator satisfies conditions given by formulas (1) to (3) given below: 0.ltoreq.X.sub.1.ltoreq.(Y.sub.1/1.5).ltoreq.10 (1) X.sub.2.ltoreq.10 (2) X.sub.2.ltoreq.Y.sub.2.ltoreq.20. (3)