An airbag apparatus for a vehicle may include: a surrounding airbag installed in a seat on which a passenger is seated, and deployed toward the passenger so as to cover an upper part and side parts of the passenger; a front airbag connected to the surrounding airbag, and laterally deployed to cover a front part of the passenger; and a behavior constraint tether extended from the front airbag to an upper portion of the surrounding airbag so as to constrain the surrounding airbag and the front airbag, and configured to constrain a forward behavior of the passenger through a tensile force.