A thin energy storage device having high capacity is obtained. An energy storage device having high output is obtained. A current collector and an active material layer are formed in the same manufacturing step. The number of manufacturing steps of an energy storage device is reduced. The manufacturing cost of an energy storage device is suppressed. One embodiment of the present invention relates to an electric double layer capacitor which includes a pair of electrodes including a porous metal material, and an electrolyte provided between the pair of electrodes; or a lithium ion capacitor which includes a positive electrode that is a porous metal body functioning as a positive electrode current collector and a positive electrode active material layer, a negative electrode including a negative electrode current collector and a negative electrode active material layer, and an electrolyte provided between the positive electrode and the negative electrode.