Provided is a secondary cell that is an improvement over the conventional art in terms of volume (energy density) and production (number of production steps). This secondary cell comprises: a first-electrode doubling as a substrate, that is sheet-shaped and demonstrates the functions of a first electrode and the functions of a substrate; a front surface-side storage layer disposed on the front surface side of the first-electrode doubling as a substrate; a front surface-side second electrode layer laminated on the front surface-side storage layer; a back surface-side storage layer disposed on the back surface side of the first-electrode doubling as a substrate; and a back surface-side second electrode layer laminated on the back surface-side storage layer.