A nonaqueous electrolyte secondary battery (100) includes a positive electrode (30), a negative electrode (40), a separator (50), a nonaqueous electrolytic solution, and a battery case (10). The positive electrode includes a positive electrode current collector (32) and a positive electrode active material layer (34). The separator includes a separator substrate (52) and a heat resistance layer (54). The separator substrate has an opposite surface opposite the positive electrode active material layer. The heat resistance layer constitutes at least a part of the opposite surface and contains a heat-resistant filler and a binder. The positive electrode active material layer has an adjacent region (X). The heat resistance layer has an opposite region (Y) opposite at least an end portion of the adjacent region. The end portion of the adjacent region is adjacent to a positive electrode current collector exposure portion (33). The opposite region contains at least a calcium salt of carboxymethyl cellulose.