An airbag apparatus for a vehicle may include an inflator, and an airbag cushion having a depressed head support portion formed in a rear portion of the airbag cushion so that when the airbag cushion may be deployed by gas supplied from the inflator, the head support portion receives a head of a passenger, and shoulder support portions protruding from lateral sides of the head support portion in a rearward direction and forming a space between the shoulder support portions to have the head support portion therebetween when the airbag cushion may be deployed, and a support tether provided in the airbag cushion and extending in a transverse direction across the shoulder support portions such that a gas path may be defined in a front portion of the airbag cushion below the support tether, the gas path guiding the gas downwards.