Abstract: Beam deflectors are important optical elements which can control the propagation direction of the beam in free space. However, with the development of miniaturization of the optical systems, conventional reflector-based mechanical beam deflectors confront a huge challenge due to their large sizes and incompatibility to the device integration. Here we propose an all-dielectric flat metasurface beam deflector which is composed of a single layer array of TiO₂ nanoantennas resting on a fused-silica substrate. Numerical simulations are performed to demonstrate that the proposed deflectors are able to efficiently deflect the incident beam for different angles with transmission efficiency higher than 80% at visible frequencies. This ultrathin all-dielectric metasurface deflector may have great potential applications in integrated optics.