A battery unit includes the following elements: a battery module that includes a plurality of battery cells and a gas discharge opening for discharging gas jetted from each of the battery cells; and a gas discharge duct in communication with the gas discharge opening and discharging the gas to the outside of the battery module. The gas discharge duct includes at least one duct outlet of which cross-sectional area of the channel in the duct outlet or the sum of cross-sectional areas of the channel in the respective duct outlets is larger than a cross-sectional area of the channel on the upstream side in the flow direction of the gas. The gas discharge duct also includes a temperature reducing member that is fixed to the periphery of the duct outlet so as to block part of the channel and reduces the temperature of the gas going through gaps.