[PROBLEMS] To cushion impact acting on an occupant who is not in a regular position. [MEANS FOR SOLVING PROBLEMS] When an abnormality occurs, an airbag device (1) inflates and expands in front of an occupant and absorbs an impact from the front of a vehicle. An airbag (2) to which gas from an inflator is supplied in an abnormality is provided with a vertical recess (2c) facing the head (Ph) of the occupant (P). The recess (2c) is located at the center, in the right and left direction of the vehicle, of an occupant restriction surface (2b) formed at a position facing the occupant (P) sitting on the seat during inflation and expansion. At least one fixed vent (2ea, 2eb) and at least one variable vent (2fan, 2fb) are provided at each of opposite sidewalls (2da, 2db). The fixed vent (2ea, 2eb) has an invariant opening area, and the variable vents (2fan 2fb) has an opening area variable depending on the sitting position of the occupant (P) during expansion. The recess (2c) and the opposite sidewalls (2da, 2db) are coupled in the airbag (2) by shape control members (3a,3b). [EFFECT] Even an occupant of out of position or an occupant not wearing a seat belt can be received relatively flexibly, and trouble caused on the occupant by the airbag is reduced.