Battery Module

An object of the present disclosure is to provide a battery module including a plurality of battery groups each having a plurality of battery cells connected in parallel, the plurality of battery groups being connected in series by bus bars, for which a clad material is not used and thus dissimilar metal welding can be avoided. To achieve the object, a first bus bar P mainly contains aluminum and is connected to positive electrode terminals of a plurality of battery cells of each battery group via welding joint portions W. A second bus bar N mainly contains copper and is connected to negative electrode terminals of the plurality of battery cells of each battery group via welding joint portions W. The first bus bar P of one of the mutually adjacent battery groups of the plurality of battery groups is connected to the second bus bar N of the other battery group via a mechanical joint portion M.