PURPOSE: To absorb low frequency radio waves efficiently by laying out a constitutional body which comprises a plurality of conductive resistor-formed radio wave absorbing materials arrayed in a laminated manner at an inner wall in a checkerboard pattern.

CONSTITUTION: A radio wave absorber is laid out in a checkerboard pattern and mounted with the inner wall side of a radio wave anechoic room at a base part of the radio wave absorber. A cone 3 is mounted with a measurement space side of the base art 2 so as to absorb the radio waves easily. Furthermore, the absorber whose portions are surrounded by the base part and exposed to the inner wall are provided with a large cone 10 formed in a similar manner to the cone 3. The cone 10 is a radio wave absorbing plate as well and formed in square cone shape. The quantity of the radio wave absorbing materials of the radio wave absorbing plate per unit area for the whole inner wall surface, is reduced uniformly in the radio wave anechoic room where the radio wave absorbers are laid out in a checkerboard pattern on the inner wall side of the base part 2. This construction makes it possible to absorb low frequency radio waves efficiently without lowering the radio wave adsorption properties.