An energy storage device comprises a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The negative electrode has a negative substrate layer, and a negative composite layer arranged on the surface of the negative substrate layer. The separator has a separator substrate layer. The negative composite layer contains a non-graphitizable carbon having a particle diameter D50 of 2.0 μm or more and 6.0 μm or less. A corrected negative electrode density, which is defined as a value obtained by dividing, by a thickness of the separator substrate layer, a value obtained by multiplying a density of the negative composite layer by a thickness of the negative composite layer, is 1.2 (g/cm3) or more and 5.1 (g/cm3) or less.