Abstract: A coaxial cable having an inner conductor including a very fine metal wire having a diameter of 120 .mu.m or below and a tensile strength of 100 kg/mm.sup.2 or above, and a plated noble metal layer coating the very fine metal wire, an insulating layer of an insulating material coating the inner conductor, an outer conductor coating the insulating layer, and a jacket coating the outer conductor. In forming the inner conductor, a metal wire is coated with a noble metal layer by plating, and then the metal wire coated with the noble metal layer is subjected to plastic working to reduce the diameter and to improve the structure of the noble metal layer, A high-frequency signal applied to the coaxial cable is transmitted through the noble metal layer of a satisfactory structure by skin effect without being disturbed. The very small diameter and very high tensile strength of the very fine metal wire of the inner conductor enables the coaxial cable to be formed in a very small diameter.