PURPOSE: To obtain a sufficient mechanical strength without lowering the radio wave absorption effect by forming a plastic added with good conductive powder or particles such as carbon, silver, aluminum or copper into a plate as a base of a synthetic resin.

CONSTITUTION: A polypropylene is used as a base resin and a conductive member of carbon fiber flakes and carbon black powder and glass fiber flakes or the like are added to form a conductive plastic plate having a thickness of 0.7mm. In comparing the radio wave absorption characteristic of the plate with that of a mica plate with vapor-deposited aluminum and a phosphorus bronze plate having a thickness of 0.2mm, the insertion loss to the orthogonal polarized component is nearly equal at ≤-0.3dB. Further, the parallel polarized component absorption factor is equal at ≥85%. Thus, in using said conductive plastic, the thickness is increased and the mechanical strength is improved without lowering the radio wave absorption effect.