A battery module includes a plurality of battery cells each having two electrode terminals, i.e., positive and negative electrode terminals; a first housing case that houses a first battery cell group; a second housing case that houses a second battery cell group; and a fixing tool that fixes the first and the second housing cases by making the electrode terminals in the first battery cell group face the electrode terminals in the second battery cell group. The second battery group is housed in the second housing case while being inclined relative to the first battery cell group, connected to the negative electrode terminal of each battery cell in the first battery cell group facing the positive electrode terminal of the battery cell, and connected to the positive electrode terminal of each battery cell in the first battery cell group facing the negative electrode terminal of the battery cell.