First-principles and semiclassical Boltzmann transport formalism are employed to investigate thermoelectric properties of β-antimonene. We obtain phonon dispersion, phonon group velocity, phonon relaxation time, lattice thermal conductivity and Seebeck coefficient, electrical conductivity and electron thermal conductivity as functions of chemical potential of β-antimonene. It indicates that longitudinal acoustic (LA), transverse acoustic (TA), and z-direction acoustic (ZA) branches of β-antimonene are linear near Γ point due to its buckling structure. Acoustic phonon contribution to whole lattice thermal conductivity is as high as 96.68%, and optical phonon accounts for 3.32% only. A large a-o gap leads to LA be dominant in group velocity and relaxation time, and thus increasing LA phonon contribution to whole thermal conductivity. In addition, merit ZT increases with temperature, and reaching a maximum of 0.275 at 700 K near Fermi level.