An optical device is provided. The optical device includes a first surface that defines a concave light incident surface facing a central axis and a light source; a second surface disposed opposite the first surface which is configured to reflect light incident on the concave light incident surface; and an inclined light exit surface between the first surface and the second surface. The second surface includes a concave first reflective portion curving toward the first surface, and a substantially flat second reflective portion which portion is interposed between a first reflective portion edge of the first reflective portion and an outer second surface edge of the second surface. The first reflective portion is configured to totally reflect light incident at a predetermined angle or more with respect to a top surface of the light source once to the light exit surface.