SIDE AIRBAG DEVICE

A side airbag device (10) includes an airbag (56) which includes a first base fabric (60) and a second base fabric (62) constituting an inflatable envelope, and in the event of a lateral collision of a vehicle, the airbag (56) is deployed between an occupant (P) and a door (30). The airbag (56) further includes a partition fabric (66) between the first base fabric and the second base fabric. The partition fabric partitions the inflatable envelope into a first inflatable compartment (92) corresponding to a shoulder (P1) of the occupant, and a second inflatable compartment (94). The partition fabric is provided with a valve mechanism which opens to connect the first inflatable compartment and the second inflatable compartment when the first inflatable compartment is fully inflated.