SIDE AIRBAG FOR VEHICLE

A side airbag for a vehicle includes: a main cushion located at a seat of the vehicle and configured to be unfolded at a front side of a passenger to a front of the vehicle when gas is injected into the main cushion; a sub cushion connected to a front-end portion of the main cushion and configured to be unfolded from the front-end portion of the main cushion toward the passenger when gas is injected into the sub cushion; a support tether having a first end connected to the seat and a second end connected to the sub cushion so as to support the sub cushion; and a cushion cover surrounding both the main cushion and the sub cushion, and having a tether slit through which the support tether passes.