AIRBAG DEVICE

The present invention obtains an airbag device that can effectively protect an upper body and knees of a passenger by a simple airbag structure. An airbag (20) that structures an airbag device (10) for a passenger's seat has a main bag (26) that restrains an upper body (U) of a vehicle passenger (P) from a front side in a vehicle longitudinal direction, a sub-bag (28) that has a smaller volume than the main bag (26) and that restrains knees (K) of the passenger (P) from the front side in the vehicle longitudinal direction, and an inner tube (38) that is folded-up together with the main bag (26) and the sub-bag (28) and is inflated and expanded within the airbag (20) by a gas supply from an inflator (22). The inner tube (38) directly supplies gas of the inflator (22) to the main bag (26) and the sub-bag (28) respectively. A check valve (40) is provided at a gas exit (38C) that communicates the inner tube (38) with the sub-bag (28).