An optical device has a light guide plate that guides light in a plane parallel to an emission surface thereof, an optical deflection surface that deflects light entering the light guide plate from a light source that faces a plane parallel to at least the emission surface or the surface opposite the emission surface, so that the light travels along the light guide direction of the light guide plate, and a plurality of light focusing portions. Each of the light focusing portions includes an optical surface whereon the light deflected by the optical deflection surface and guided by the light guide plate is incident, and which causes the emission surface to output emission light that converges substantially on a convergence point or convergence line in a space, or that radiates substantially from a convergence point or convergence line in a space.