A method of manufacturing an optical fiber, comprises applying a UV cured resin to an outer circumference of a running glass optical fiber, forming an accompanying flow composed of an inert gas near a surface of the resin by passing the glass optical fiber immediately after having the resin being applied through an atmosphere of the inert gas, and forming a coating by irradiating the resin coated with the accompanying flow with ultraviolet ray to cure the resin while the glass optical fiber accompanied by the accompanying flow is passed through a UV transmission tube to which a gas containing oxygen is supplied.