Micromachining of an optical fiber was carried out in CF4 plasma by reactive ion etching (RIE) system consisting of two parallel-plate electrodes and a rotary motion feedthrough. The cathode was powered by a rf generator at 13.56 MHz and was covered with a quartz plate in order to prevent sputtering of nonvolatile compounds from the cathode. During the etching, the rotation of the optical fiber could be controlled from outside the vacuum chamber. The diameter of the etched optical fiber was reduced from 125 μm to 50 μm by RIE for 8 hours under the condition of 13 Pa pressure and 150 W rf power. The other processes such as the sharpening of the fiber tip were also described.