In a high-frequency coaxial cable (1), an internal solid layer (3), an insulation layer (4) made of a foam resin, an external solid layer (5), and an external conductor (6) are provided on the periphery of an internal conductor (2) in this order. The external solid layer (5) has a dielectric dissipation factor of 1.0×10−4 or less at 2 GHz. Thereby, the voltage standing-wave ratio and the attenuation of the high-frequency coaxial cable (1) are reduced.