The silver halide fiber for transmitting a CO2 laser beam using the mixture crystal of silver bromide and silver chloride is described. The silver halide is purified by zone melting. The absorption coefficient of its preformed crystal measured by a CO2 laser calorimeter is less than 1.0x10-4 cm-1 . The silver halide fibers whose diameters are 0.5 to 0.7mm are made by hot extrusion. The transmission loss of silver halide fiber is 0.07dB/m when measured by a CO2 laser beam. The measured spectral transmission lgss due to scattering inside and on the surface of the fiber is nearly proportional to λ -2 where λ is the wavelength, and it is low in the infrared wavelength region, ranging from a few microns to over ten microns. Because of its excellent resistance to optical damage and bending as well as other characteristics important to practical application, silver halide fiber is suitable for use in CO2 laser power transmission. It is also expected to he an optical waveguide in the field of infrared optic sensors.