[Problem] To provide a side airbag apparatus capable of quickly and properly restraining a passenger in the initial stage of deploying an airbag, along with a passenger protection apparatus including this.
[Resolution means] A side airbag apparatus according to the present invention includes: an airbag for restraining a passenger when expanded and deployed; and an inflator for supplying expansion gas to the airbag. The airbag includes: a first chamber which houses the inflator and is deployed outside in the vehicle width direction of the frame side wall part; and a second chamber which is deployed inside in the vehicle width direction of the frame side wall part. In addition, the first chamber is deployed such that at least a portion thereof, as seen from the vehicle side, overlaps the frame side wall part. At this time, the rear end part of an expanding region of the second chamber, as seen from the vehicle side, is formed in front of the rear end part of the first chamber.