PURPOSE: To obtain a radio wave absorber which has nearly the same characteristic as a conventional one by a method wherein glass, which is foamed in small bubbles, is impregnated with carbon so as to prevent it from deforming.

CONSTITUTION: Glass 1 foamed in small bubbles is impregnated with carbon 2. The glass 1 has the same impedance as the air, so that a material, which has almost the same characteristic as a conventional radio absorber, can be obtained. The radio wave absorbing mechanism of the absorber of this design is the same as that of a conventional one and such that it is based on conversion of electric energy into thermal energy through the resistance of the carbon 2. By these processes, the radio wave absorber, which is prevented from deforming and has characteristic equivalent to that of a conventional one, can be obtained.