To provide a radio wave anechoic box capable of measuring the characteristics of an object to be measured for radiating electromagnetic waves at a plurality of frequency bands.

A cylindrical member 7 capable of moving axially is provided inside a metal casing 2 and a screen member 12 capable of moving axially is provided in the cylindrical member 7. Then, radio wave absorbers 3, 5, 14 for absorbing electromagnetic waves at a frequency band of a high-frequency side are provided on a front wall surface 2A of a metal casing 2, on an inner-periphery surface, and on the front of the screen member 12, respectively. Radio wave absorbers 4, 11, 15 for absorbing electromagnetic waves at a frequency band of a low-frequency side are provided on a rear wall surface 2B of the metal casing 2, on an inner-periphery surface of the cylindrical member 7, and on the rear surface of the screen member 12, respectively. Therefore, by moving the cylindrical member 7 and the screen member 12 axially, either the radio wave absorbers 3, 5, 14 or radio wave absorbers 4, 11, 15 can be exposed to the metal casing 2 selectively.