An optical element is made of a transparent medium L1 that has a view angle of about 90° at a side in a cross section including the central axis 2 thereof and as viewed from a direction orthogonal relative to the central axis 2 and is rotationally symmetric relative to the central axis 2 with a refractive index greater than 1, in which the transparent medium L1 has a first transmissive surface 11 arranged at the outermost periphery relative to the central axis 2, a first reflective surface 12 arranged at the side of the central axis 2 relative to the first transmissive surface 11, a second reflective surface 13 arranged at the side opposite to the image plane 5 relative to the first reflective surface 12 and a second transmissive surface 14 arranged at the side of the image plane 5 relative to the second reflective surface 13, the flux of light entering the transparent medium L1 proceeds through it by way of the first transmissive surface 11, the first reflective surface 12, the second reflective surface 13 and the second transmissive surface 14 to form a substantially Z-shaped optical path A in the order of forward ray tracing before going out from the transparent medium at the side of the image plane 5, and the optical path A is formed only at a side relative to the central axis 2.
