This optical device is provided with a light guide plate which propagates light from a light source in a plane parallel to an emission surface, and with multiple light deflecting units which are arranged two-dimensionally in the plane parallel to the emission surface and which deflect the light propagated through the light guide plate and emit light from the emission surface to form an image in space. In the plane parallel to the emission surface, the multiple light deflecting units expand light incident to said light deflecting units into light that has an intensity distribution correspondingto an image in the direction perpendicular to the light guide direction of the light guide plate and emit said light from the emission surface, and thereby, light in a direction diverging from the image is formed through light collecting from the multiple light deflecting units arranged along a direction perpendicular to the light guide direction.