A battery unit equipped in a vehicle includes a battery, a case accommodating the battery, an upper surface covering material covering an upper surface of the battery in the case, an intake portion provided on the upper surface covering material and configured to take in air from an outside of the case to above the battery, a lower surface covering material covering a lower surface of the battery in the case, an exhaust portion provided on the lower surface covering material and configured to discharge air that has cooled or heated the battery, a fan disposed below the lower surface covering material, configured to take in air discharged from the exhaust portion, and discharge the air between the lower surface covering material and a bottom surface of the case.