A module battery comprises cells each having an electric power generating element hermetically sealed in a package film, and cell holders on each of which each of the cells is mounted and held. The cell holders are formed in configurations so as to allow the cell holders to be freely stacked in a plurality of stages while permitting the cells to be retained thereon and to allow electrode tabs of the cells to be exposed between the cell holders neighboring in a stacking direction. Thus, the module battery can be formed in an easy assembly work.