In a method for forming a hole for fitting an optical fiber only at a core portion without having to precisely match or accord the focus of a laser beam with the end surface of an optical waveguide, when a laser beam is irradiated onto the end surface of the optical waveguide, the focus of the laser beam is turned away from the end surface of the optical waveguide and a region of the irradiation includes the core and the periphery thereof. Thereafter, the energy of the laser beam is increased step by step, and a few pulses thereof are radiated with the intensity fixed when ablation occurs at the core portion, so that the hole is formed only at the core portion.