The phase and group velocities of high-order Gaussian beams in vacuum are deduced from the phase shift, and the relations between the two velocities and the additional phase shift is discussed. It is confirmed that the beam waist radius is proportional to the square root of wavelength by comparing the group velocities on three different premises. The phase velocity can be larger than c in vacuum, and the hyperbolic surface of the beam radius is just the boundary of the superluminality and subluminality. While the group velocity is equal to c along the beam axis and smaller than c off the axis on the rational premise.