To provide a method for changing absorbing band in an electromagnetic wave absorber by which the frequency band to which a high electromagnetic absorbing property is required can be changed by changing parameters while keeping a basic construction.

An absorber 1 comprises a conductive rubber 5 in which multiple holes 5a of inner diameter corresponding to the wavelength of microwave are formed at a specified open area ratio, a ferrite rubber 9 which is placed on the conductive rubber 5 through a dielectric layer 7 and is formed of at least two-layer ferrite rubber sheets 9a and 9c containing ferrite powder at a specified proportion, and an open ferrite rubber sheet 9b in which multiple holes of inner diameter corresponding to the wavelength of microwave are formed at a specified open area ratio which is placed between the ferrite rubber sheets 9a and 9c and a metal reflecting plate 3. In this case, the thickness of the dielectric layer 7 is variably adjusted in accordance with the microwave band to be absorbed.