Abstract: Disclosed is a laser beam machining method and apparatus for irradiating a work with a laser beam, to melt-evaporate the irradiated region of the work at the irradiation spot. According to the invention, a work such as an optical fiber can be machined into a complicated form within a short period of time without accurately controlling the laser beam irradiation position while inhibiting the decline of machining accuracy due to thermal effect, by using a mask having a light-transmitting section that is predetermined times as large as the laser beam machining spot corresponding to the form of the portion undergoing melt-evaporation of the work.