An energy storage device includes a positive electrode provided with a positive composite layer containing a positive active material, a negative electrode provided with a negative composite layer containing a negative active material, and a separator partitioning between the positive electrode and the negative electrode, wherein the separator includes a substrate uniaxially drawn into a sheet shape and a coating layer coating at least one of surfaces of the substrate, and the coating layer has an anisotropic structure with orientation in a direction different from a drawing direction of the substrate.