A secondary cell module and the method of its production, which comprises a combination cell formed by connecting the positive and/or the negative electrode terminal(s) of multiple secondary cells in series and/or in parallel with each other through a metal bus-bar and a casing which contains the combination cell, wherein the secondary cell is formed in a sheet shape and comprises sheet-type internal electrode couple, electrolytic solution and a flexible outer wrapper of envelope type which contains them in a sealed state. The secondary cell module is of a simple structure and it can be small-sized and light-weighted or thin-shaped as necessary and the heat which generates inside the cell can be efficiently diffused to outside, thereby enabling the production of cells of high capacity with a high degree of freedom in designing its shape as well as supreme productivity.