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 20P mainly contains aluminum and is connected to positive electrode terminals of a plurality of battery cells 1 of each battery group 10 via welding joint portions W1. A second bus bar 20N mainly contains copper and is connected to negative electrode terminals of the plurality of battery cells 1 of each battery group 10 via welding joint portions W2. The first bus bar 20P of one of the mutually adjacent battery groups 10 of the plurality of battery groups 10 is connected to the second bus bar 20N of the other battery group 10 via a mechanical joint portion M.