Recently, it is demonstrated that the subwavelength grating (SWG), which is the surface-relief grating with the period smaller than the wavelength of light, behaves as an antireflection surface. In particular, a tapered SWG suppresses reflection over a wide spectral bandwidth. The SWS is more stable than the multulayered thin film, since it is fabricated from a single material. In this study, we demonstrate broadband antirefraction properties of III-V materials (GaSb) by using SWG. The surface nano-structures with 200-350nm periods are fabricated by means of electron beam lithography and fast atom beam (FAB) etching. The reflectivity of the sample is strongly suppressed from the visible to near IR region. The experimental data is compared with numerical simulations using the rigorous coupled analysis (RCWA).