PURPOSE: To provide an optical fiber capable of easily confirming the position of a diffraction grating formed by the change of an optically induced refractive index and its manufacturing device and method therefor.

CONSTITUTION: This optical fiber manufacturing device is the device manufacturing an optical fiber 15 by the line drawing from a preform 10 and is provided with a diffraction grating forming device 30 forming a diffraction grating by irradiating the optical fiber 14 subjected to the line drawing with an interfered ultraviolet ray, a marking device 44 marking a mark on the surface of the optical fiber passing a hardening furnace 18 and a moving amount detecting means 46 detecting the moving amount of the optical fiber. A control device 28 can actuate the marking device 44 so as to mark a mark on the prescribed position with respect to the diffraction grating formed by the diffraction grating forming device 30 on the basis of the moving amount of the optical fiber detected by the moving amount detecting means 46. Thus, the mark indicating the position of the diffraction grating is marked on the produced optical fiber 15.