A battery module joined to a joint body comprises a plurality of battery cells and a plurality of heat transfer plates each provided between adjacent battery cells. Each of the heat transfer plates has a portion-to-be-sandwiched provided between adjacent battery cells and a portion-to-be-joined joined to the joint body and having a facing surface facing the joint body. A first heat transfer layer touching each of the battery cells and having a first thickness is provided on the portion-to-be-sandwiched of each of the heat transfer plates. A second heat transfer layer is provided on the facing surfaces of at least the heat transfer plates other than the heat transfer plate that is the nearest from the joint body when the portion-to-be-joined is joined to the joint body. The second heat transfer layer is configured so as to touch the joint body. The second heat transfer layer provided on the heat transfer plate that is the furthest from the joint body when the portion-to-be-joined is joined to the joint body has a second thickness thicker than the first thickness.