SIDE AIRBAG

A side airbag that is configured to reduce risk of injury to a passenger by differentiating inner pressures in an airbag cushion at the beginning of a deployment of the airbag cushion. The side airbag includes a diffuser configured to supply gas discharged from an inflator to an inside of an airbag cushion, a separator partitioning an internal space of the airbag cushion up and down so that an upper region of the airbag cushion is more rapidly inflated than a lower region of the airbag cushion by the gas introduced into the airbag cushion through the diffuser, and a passage formed between the upper region and the lower region such that the gas flows between the upper region and the lower region.