An airbag device includes an airbag that is deployed in front of a passenger's seat of a car, and an inflator for supplying gas to deploy the airbag. The airbag includes a lower bag segment for holding shoulders and a chest of an adult passenger when it is deployed, an upper bag segment that rises from the lower bag segment so as to hold a head of the adult passenger when it is deployed, and a partition cloth having an inner vent hole for separating the lower and upper bag segments. The inflator supplies the gas directly to the lower bag segment, and then to the upper bag segment through the inner vent hole.