PURPOSE: To provide an optical fiber coupler capable of producing an optical fiber coupler with prescribed characteristic with superior reproducibility.

CONSTITUTION: Fnsion drawing is performed as measuring light output from the output terminals of optical fibers f1, f2. When light is inputted from the optical fiber f1, the fusion drawing is stopped when the light output from the output terminal of the optical fiber f1 arrives at a value in which the maximum value P2 of the light output is multiplied by a prescribed ratio r2 larger than 50%. Or, when the light with specific two wavelength are inputted from the output terminals of the optical fibers f1, f2, respectively, the fusion drawing is stopped when the difference of the light output from the output terminals of the optical fibers f1, f2 arrives at a value in which the maximum value P3 of the difference of the light output is multipled by a prescribed ratio r4 larger than 0% and also smaller than 50%.