A method of fabricating a one-way transparent optical system by which external light is effectively intercepted and internal light passes nearly without loss is provided. The method includes: forming a photoresist on an upper surface of a transparent substrate; heating and carbonizing the photoresist to form a black body layer; patterning the black body layer to form a plurality of light-absorbing materials on the transparent substrate; and forming protrusion structures having a shape of a convex lens shape for refracting incident light toward a corresponding light-absorbing material of the light-absorbing materials, on the transparent substrate on which the light-absorbing materials are formed.