A variable control apparatus for an airbag of a vehicle includes: a plurality of tethers each of which having one side coupled to a front sheath among a plurality of sheaths of an airbag cushion, each of the plurality of tethers formed to have a length shorter than a distance between the front sheath and a rear sheath when the airbag cushion is fully deployed; a release mechanism provided at a rear sheath side of the airbag cushion, connected to the respective other sides of the plurality of tethers, and selectively releasing a tether among the plurality of tethers upon an operation of the release mechanism; and a controller configured to variably control a deployment shape of the airbag cushion by operating the release mechanism based on a collision direction of the vehicle, a seat state of a seat of the vehicle, or a sitting posture of a passenger in the vehicle.