A secondary battery comprising a power generating part and a charging part, wherein the power generating part comprises an acidic medium in which a first electrode is disposed and a basic medium in which a second electrode is disposed; the acidic medium and the basic medium are disposed adjacent to each other; at least one of the acidic medium or the basic medium includes at least one reactive substance; and the charging part comprises a reactive substance regenerating device which regenerates the reactive substance from power-generation products produced by electric power generation in the power generating part.