To obtain a radio wave absorber, which is thinner than a conventional pyramid type, for a relatively wide band where the frequency range is limited.

With respect to the radio wave absorber consisting of absorbents 11 to 16 and a conductor 20, absorbents 11 to 16 are so constituted that the magnitude of a complex permittivity in absorbents 11 to 16 may be reduced to a minimum level from the space side toward the conductor side and successively may be increased toward the conductor thereafter at the incidence of a radio wave from the space to absorbents 11 to 16 lined with the conductor 20. Preferably, absorbents 11 to 16 comprise a plurality of layers, and each layer of absorbents 11 to 16 consists of a high-permittivity material containing a conductor by a certain content and a low-permittivity material, and the high- permittivity material is a composite where a material like sponge contains the conductor, and the low-permittivity material is a material like sponge.