  Lorentz transformation of three-qubit Greenberger-Horne-Zeilinger (GHZ) state
is studied. Also we obtain the relativistic spin joint measurement for the
transformed state. Using these results it is shown that Bell's inequality is
maximally violated for three-qubit GHZ state in relativistic regime. For
ultrarelativistic particles we obtain the critical value for boost speed which
Bell's inequality is not violated for velocities smaller than this value. We
also show that in ultrarelativistic limit Bell's inequality is maximally
violated for GHZ state.
