Abstract: The present invention provides a manufacturing method for an optical fiber coupler, the optical characteristic of which is less dependent on wavelength. In the manufacturing method, a coupling region is formed by fusion-bonding and extending parts of a plurality of optical fibers arranged to be closely touching each other. At least one of the optical fibers is extended at a speed different from that of the other optical fibers when a low-temperature heat source is applied to soften the optical fibers. When the temperature of the low-temperature heat source is raised to form a high-temperature heat source, the extended parts of the closely touching optical fibers are fusion-bonded. When the temperature of the high-temperature heat source is then lowered to form a low-temperature heat source again, the fusion-bonded part can be extended further. In one embodiment, the fibers are twisted before fusion bonding the fibers.