A battery and a manufacturing method thereof are provided. The battery module includes: a battery cell group, in which a plurality of battery cells is laminated; a pair of end plates, which is arranged on two end portions of the battery cell group; and restraint members, which are disposed over the pair of end plates and restrain the battery cell group between the pair of end plates. The restraint members are coupled by grappling structures to the pair of end plates on two end portions along the lamination direction the battery cells, and the pair of end plates clamps the battery cell group in a state that the battery cell group is compressed and pulling forces toward opposite directions act on the two end portions of the restraint members by a restoration force when the battery cell group restores from the compression state.