SEAT AIRBAG DEVICE FOR VEHICLE

A seat airbag device for a vehicle is proposed. The seat airbag device for a vehicle includes: a main chamber located in a vehicle seat at a side portion of an occupant and configured to be deployed toward a front portion of the vehicle when gas is injected thereinto; a sub-chamber connected to a front end of the main chamber and configured to be deployed in a direction intersecting a deployment direction of the main chamber when the gas is injected thereinto; and an expansion portion expanded from the front end of the main chamber and connected to an upper portion or a lower portion of the sub-chamber.