A thinner secondary battery can be provided by a thin secondary battery characterized by comprising a battery element obtained by stacking positive electrode layers, electrolyte layers and negative electrode layers and laminates sealing front and back surfaces of the battery element, wherein the laminates each are made of a stacked body constructed of at least an adhesive layer and a metal layer in the order from the battery element side and the metal layer in the front surface side of the battery element and the metal layer in the back surface side thereof are different from each other in strength or thickness, or both of them.