An optical fiber processing apparatus comprises reactors (3, 3a, 3b and 3c) that accommodate optical fiber, a single suction pump (7) having an intake port (19) and an outlet port (21), a storage chamber (5) into which deuterium containing gas is delivered, and a circuit portion (9, 59) including a plurality of valves disposed on a plurality of passages connecting the reactors, the suction pump and the storage chamber. The circuit portion includes a first channel for returning deuterium containing gas inside a reactor chamber to the storage chamber, a second channel for delivering air to the reactor chamber thereby rendering the pressure inside the reactor chamber atmospheric pressure, a third channel for decompression of the reactor chamber and a fourth channel for supplying deuterium containing gas in the storage chamber into the reactor chamber.