An electric storage device having a multilayer body in which a separator layer is provided between a positive or negative first electrode and a second electrode of the opposite polarity to the first electrode, an electrolyte, and a package that holds the multilayer body and the electrolyte, and includes at least two first-polarity compound sheets, each configured by integrating a first-polarity collector electrode, a first-polarity active material layer provided on one main surface of the first-polarity collector electrode, and a separator layer that covers at least part of the one main surface. Another main surface of the first-polarity collector electrode in one of the at least two first-polarity compound sheets and another main surface of the first-polarity collector electrode in another of the first-polarity compound sheets are opposed to each other and joined via a joining layer. The joining layer contains a high-polymer having imide coupling in its main chain.