To make it possible to produce the terminal part of a coated optical fiber in a short time, to prevent the direct adhesion of dust, etc., on the end face in the exposed part of the optical fiber and to prevent the adverse influence by moisture by forming a carbon layer on the outer side of the front end part of the optical fiber in this terminal part.

The coating layer 2 in the terminal part of the coated optical fiber 3 constituted by forming the coating layer 2 on the outer side of the coated optical fiber 1 is removed by a prescribed length, by which the exposed part 4 of the optical fiber is formed in the non-reflection terminal part of the coated optical fiber 3. The end face of the exposed part 4 of the optical fiber is cut perpendicularly to the longitudinal direction. A carbon layer 9 is densely formed on the outer side of the exposed apart 4 of the optical fiber. Further, the exposed part 4 of the optical fiber and the carbon layer 8 formed on the outer side of the exposed part 4 of the optical fiber are housed into a ferrule 5 consisting of ziroconia, etc. An adhesive is applied on the inside of the ferrule 5, by which the ferrule 5 and the coated optical fiber 3 are adhered and fixed.