A battery unit mounted on a vehicle includes a case having an intake port, a battery module which is disposed inside the case and in which a plurality of battery cells are stacked, a fan disposed inside the case and blowing cooling air to the battery module, and an intake duct connecting the intake port and the fan. The intake duct includes a first flow path extending along a first surface of the battery module, and a second flow path extending along a second surface different from the first surface of the battery module.