Provided is an energy storage device which employs the use of a separator provided with a layer having poor thermal properties such as a heat resistant coated layer and is capable of inhibiting a decrease in performance. The energy storage device includes: a wound body including a positive electrode, a negative electrode, and separators which are layered and wound, the separators being interposed between the positive electrode and the negative electrode and having a first surface and a second surface, the first surface having thermal bonding properties superior to thermal bonding properties of the second surface; and an insulation sheet wound around an outermost layer of the wound body. At least one of the separators is bonded to the insulation sheet via the first surface thereof.