An airbag apparatus for a vehicle may include an inflator; a housing installed in a roof, and a cushion contained in the housing and configured to be deployed downwards by a gas discharged from the inflator to protect an occupant in the vehicle, wherein an upper surface of the cushion is supported by the roof when the cushion is in a deployed state, and a front surface of the cushion extends in a rear direction of the vehicle in an inclined shape to form a recess to prevent interference with a seatback of the front seat while the cushion is deployed downwards.