PURPOSE: To provide a coated optical fiber having high quality by coating the surface of an optical fiber with a recoating resin in a reduced pressure atmosphere at the time of recoating of the optical fiber.

CONSTITUTION: An exposed part 2 of the fusion-spliced optical fibers is inserted into a through-hole of a mold 3 and fixed. A container 8 contg. the recoating resin 7 and a resin injection hole 4 are connected by a tube 11. A pressure reducing hole 5, a pressure reducing device 10 and a differential pressure gage 9 are connected by a pipe 12. The container 8 is compressed to inject the recoating resin 7 into the space in the through-hole. The gas existing in the space in the through-hole is discharged to the pressure reducing device 10 side as the recoating resin 7 flows therein. Next, the recoating resin 7 is cured by irradiating the resin with UV rays through the mold 3 made of a transparent plastic in this state and thereafter, the operation of the pressure reducing device 10 is stopped.