A battery pack which can increase of the volumetric efficiency of the battery pack without being contained in a resin mold case is provided. A first laminate material has a concave portion formed by drawing where a battery element is contained. A second laminate material is stacked so as to cover the opening of the concave portion to seal up the periphery of the opening. The first and second laminate materials are bend inwards so as to cover the battery element, and bonded and fixed together by heating. The first laminate material has three-layer structure including a polypropylene layer, a soft aluminum layer, and a nylon layer or PET layer. The second laminate material has a similar structure but includes a hard aluminum layer. Therefore, the second laminate material has enough strength to resist deformation without being contained a cell in a resin mold case.
