Extremely flexible hollow fibers with 50 μm-bore size were developed for infrared laser light delivery. The hollow fiber was inner coated with silver and a dielectric layer to enhance the reflection rate at an objective wavelength band. The silver layer was inner-plated by using the conventional silver mirror-plating technique. Concerning the fabrication parameters used up to now for 320-μm bore-sized fibers, the target flowing rate for plating solutions was 10 ml/min. Parallelly arranged bundles of silica capillary were used to increase the cross-sectional area. To achieve the target, bundles with 4800 pieces were used for the capillary with a length of 20 cm and inner diameters of 50 μm. The loss for the 50 μm bore size, 10 cm length silver hollow fiber was 6 dB at the wavelength of 1 μm. Thin dielectric layer was formed by using liquid-phase coating method for low-loss transmission of Nd:YAG and Er:YAG laser light.