A 360 degree viewing angle lens unit, from the object side to the image side thereof, includes a 360 degree viewing angle lens and a relay lens. The viewing angle lens includes an annular incident surface, a first reflective surface, a second reflective surface, and an emitting surface. The annular incident surface has a positive radius of curvature and symmetrically concentric around an optical axis of the lens unit. The first reflective surface has a positive radius of curvature and is symmetrically concentric around the optical axis. The second reflective surface has a negative radius of curvature, and is coaxial with the incident surface. The emitting surface has a positive radius of curvature and is coaxial with the first reflective surface. The relay lens has a positive refractive power and is aligned with the emitting surface. The relay lens is configured for condensing image light output from the emitting surface.