Provided is an energy storage device which employs 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 (121) which is made by imposing and winding a positive electrode (122), a negative electrode (123) and separators (124, 125) which interposed between the positive electrode and the negative electrode and have two surface having different thermal bonding properties; and an insulation sheet (127) wound around an outermost layer of the wound body (121). At least one of the separators (124, 125) is bonded to the insulation sheet (127) via the first surface with better thermal bonding properties.