Provided is a battery unit capable of reducing the size of vehicle installation space by being more compact. A battery unit equipped with: a plurality of battery modules each containing a plurality of battery cells which are connected in parallel with one another, and each having a duct chamber for discharging gas emitted by the battery cells; and a fixing member for fixing the plurality of battery modules to the wall of a storage case in a manner such that the modules are integrally assembled with one another. The fixing member has an attachment part which attaches to a module case, and the attachment part includes an exhaust duct part for collecting and discharging the gas emitted into the duct chamber of each battery module.