An optical device has a light guide plate configured to guide light within a plane parallel to an emission surface thereof, and a plurality of optical deflectors arranged two-dimensionally within a plane parallel to the emission surface. Each of the optical deflectors deflects light propagating through the light guide plate, and causes the emission surface to output light forming an image in a space. Each of the optical deflectors is configured to spread the light incident thereon that has an intensity distribution corresponding to an image in a direction orthogonal to the light guide direction of the light guide plate in a plane parallel to the emission surface, and cause the emission surface to output the light which groups the light from the plurality of optical deflectors arranged along a direction orthogonal to the light guide direction, such that light radiating from the image is formed.