Provided is an optical modulating device including an incidence optical system, an optical modulating assembly including a plurality of nano-antennas that form a meta-grating based on a driving signal, the optical modulating assembly being configured to change a traveling direction of incidence light incident at an incidence angle from the incidence optical system based on an effective displacement of the meta-grating according to the driving signal, and an emission optical system configured to emit light steered by the optical modulating assembly, wherein the emission optical system is further configured to emit first-order diffraction light of the incidence light based on the meta-grating.