A vehicle-mounted battery apparatus to be mounted in a vehicle includes: a battery pack, the battery pack including a battery cell, the battery cell including a gas exhaust portion configured to discharge internal gas; a smoke exhaust duct connected to the battery pack and configured to discharge gas to an outside of the vehicle; and a check valve disposed in the smoke exhaust duct and configured to block flow of gas from the outside of the vehicle toward the battery pack. The check valve includes: a valve seat disposed in the smoke exhaust duct and having a hole; a valve body configured to be seated on the valve seat to cover the hole; and a shock absorbing member disposed between the valve body and the valve seat to alleviate impact of the valve body against the valve seat.