A foam coaxial cable includes a central conductor; an inner skin layer surrounding the central conductor coaxially; an insulation layer surrounding the inner skin layer coaxially and made of polyethylene resin containing a plurality of foam cells uniformly formed therein; wherein the inner skin layer is made of polyolefin resin having excellent compatibility with the polyethylene resin to increase an interfacial adhesive force with the insulation layer, an outer skin layer surrounding the insulation layer coaxially to prevent overfoaming of the insulation layer and allow uniform creation of foam cells; a shield surrounding the outer skin layer coaxially; and a jacket surrounding the shield. This cable improves an interfacial adhesive force between the central conductor and the insulation layer and also improves the degree of foam of the foam cells, thereby capable of propagating ultra high frequency of GHz level without signal interference.