An airbag device for a car may include an inflator positioned between first and second seats and generating an operating gas, a chamber part receiving the operating gas generated by the inflator and expanding between the first and second seats, a tether part connected to the chamber part to control a deployment shape of the chamber part, and a locking release part connected to the tether part at an inner surface or side surface of the chamber part which removes the connection to the tether part according to a control signal.