Provided is a secondary cell which has an all-solid-state secondary cell structure comprising a storage layer sandwiched between a positive electrode layer and a negative electrode layer, and which is superior to conventional secondary cells with respect to capacity, manufacturing characteristics and/or positioning. This secondary cell is characterized by having a folded single-layer secondary cell, which is formed by folding in two or in four a sheet-shaped single-layer secondary cell comprising a storage layer sandwiched between a positive electrode layer and a negative electrode layer. Improved current capacity and/or higher terminal voltage is achieved by arranging multiple folded single-layer secondary cells in a row and placing neighboring folded single-layer secondary cells either in direct electrical contact or in contact across a positive electrode member or a negative electrode member.