A battery in which the relative positions of a cathode, an anode and a separator are maintained with high precision is provided. A cathode and an anode face each other with a polymer electrolyte including a polymer and a separator in between. In each of the cathode and the anode, an active material layer is disposed on a current collector. Exposed regions where the active material layers are not disposed on the current collectors and the separator are adhered to each other with the polymer electrolyte in between. Thereby, even under a high-temperature environment, the heat shrinkage of the separator can be prevented, and heat generation due to the generation of a short-circuit current can be prevented.