An optical fiber device comprises a core and a cladding, the core being made of an optical material having a refractive index n.sub.1, and the cladding being made of an optical material having a refractive index n.sub.2, the end of the optical fiber from which light radiates forming a plane that is inclined to the fiber axis by an angle .theta., a light reflective layer being formed at least on the outer periphery of said radiating end, and the two reractive indices n.sub.1 and n.sub.2 satisfying the following relation (1):n.sub.1 -n.sub.2 .gtoreq.0.01 (1).