A nonaqueous electrolyte secondary battery according to an embodiment includes an electrode assembly, a nonaqueous electrolyte, and a prismatic battery case accommodating the electrode assembly and the nonaqueous electrolyte. The mass energy density of the secondary battery is not less than 200 Wh/kg. The nonaqueous electrolyte secondary battery further includes a non-cellular elastic sheet disposed between the electrode assembly and the battery case. The ratio (A/B) of the thickness (A) of the elastic sheet at 100% SOC to the thickness (B) of the elastic sheet at 0% SOC is 0.05 to 0.3.