To obtain a lightweight dielectric foam useful as a material for various kinds of dielectric substance antenna, etc., a spherical dielectric substance lens, etc., using the principle of Luneberg lens applicable for a radar radio reflector, an antenna, etc.

This composite dielectric foam is characterized in that a polyurethane foam is cut or ground to give chips, which are uniformly compounded with dielectric substance ceramic, integrated with a binder and adjusted to 0.5-0.04 g/cc bulk density.