Side airbag device for vehicle

A side airbag device for a vehicle comprising:

• a gas generator provided to a vehicle seat, the gas generator activated so as to generate gas for inflation and deployment;
• and
• a side airbag partitioned by a front-rear partition in a sheet shape into a front bag section and a rear bag section, the side airbag housed in a folded-up state in a side section of a seat back of the vehicle seat, the side airbag brought to inflate and deploy toward a vehicle front direction of the side section by supplying the gas for inflation and deployment into each of the bag sections,
• wherein
• in a flat developed state of the side airbag, the front-rear partition is folded into two in a manner as to protrude toward the rear bag section along a folded portion thereof located at a center portion in a width direction, and a stretchable member is extendingly disposed across between the front-rear partition and a rear end of the rear bag section, and in an inflating and deploying state of the side airbag, the stretchable member is stretched so as to restrict inflation in a vehicle front-rear direction of the rear bag section.