Abstract: A battery module includes a plurality of battery blocks connected in series. Each battery block includes a plurality of batteries connected in parallel, and each battery includes a release portion through which a gas generated in the battery is released. Each battery block includes a holder in which the batteries are housed with the release portions oriented in the same direction, a bus bar provided over the holder and connecting in parallel electrodes of the batteries, a lid provided over the bus bar and defining therebetween an exhaust chamber through which the gas released from the release portions is released outside the battery block. The lids of at least two of the battery blocks are physically connected to each other. Each lid is made of aluminum or a material having an ionization tendency greater than that of aluminum, and the bus bar is made of copper.