To provide a radio wave absorber exhibiting good radio wave absorbing performance in microwave band and millimeter wave band.

This radio wave absorber comprises the laminate of a radio wave reflection layer 1, a first absorption layer 2 of plastic reinforced with silicon carbide fibers having electrical resistivity of 0.5-2.5 Ωcm, a second absorption layer 3 of plastic reinforced with silicon carbide fibers, having electric resistivity of 103-107 Ωcm, and a third absorption layer 4 of a material having permittivity of 5 or less and dielectric loss tangent of 0.1 or less.