PURPOSE: To reduce the weight of a radio wave absorber significantly while its radio absorption performance is maintained at a high level by a method wherein rubber compound containing a specific weight ratio of mixture of ferrite powder and carbon black whose iodine adsorption rate and dibutylphthalate oil absorption rate are in specific ranges and which is mixed with a specific weight ratio to the ferrite powder is employed.

CONSTITUTION: A radio wave absorber is made of rubber composition containing 35∼55 weight % off mixture of ferrite powder and carbon black whose iodine absorption rate is 100∼150mg/g and whose dibutylphthalate oil absorption rate is 70∼140cm3/100g and which is mixed with the weight ratio of 0.54∼3 to the ferrite powder. The radio wave absorber has especially the radio wave bsorption performance not lower than 20dB, the matching thickness not larger than about 2.00 at 9.41GHz, the specific gravity not larger than about 1.70 and the weight not larger than about 3.45 at 9.41GHz.