PURPOSE: To manufacture an optical fiber having accurately controlled characteristics, easily, by measuring various characteristics of the produced optical fiber, and feeding back the values to various control parameters for the manufacture of the optical fiber.

CONSTITUTION: The optical fiber preform 41 produced in the preform-producing part 40 is heated and drawn in the drawing part 42, and the produced optical fiber 48 is transferred to the measuring part 44. The physical values relating to the cross-sectional dimensions and the refractive index distribution of the optical fiber 43 are measured in the measuring part 44, the obtained signals are processed, and the data are fed back to the preform-producing part 40 and the drawing part 42 to control the manufacture parameters influencing the cross- sectional dimensions and the refractive index distribution of the optical fiber. Since the characteristics of the optical fiber are fed back without delay to various controlling manufacture parameters, an optical fiber having accurately controlled characteristics can be manufactured in high stability.