A battery module joined to a joint body. Each heat transfer plate of the battery module has a sandwiched portion provided between adjacent battery cells and a joined portion. A first heat conductive layer that contacts a battery cell and has a first thickness is provided on the sandwiched portion of each heat transfer plate. A second heat conductive layer is provided on the facing surface of each heat transfer plate other than the heat transfer plate that is the closest to the joint body when the joined portion is joined to the joint body. The second heat conductive layer is configured to contact the joint body. The second heat conductive layer on the heat transfer plate that is the farthest from the joint body when the joined portion is joined to the joint body has a second thickness, which is greater than the first thickness.