To provide an electromagnetic wave absorber which is excellent in an electromagnetic absorption property, is light in weight, and is good in productivity.

The electromagnetic wave absorber contains a boron solid-solution carbon black and a soft magnetic material in an organic binding material. The boron solid-solution carbon black is preferred to be 0.1 Ωcm or less in the electric resistance on JISK 1469. It is preferable that the mean particle aspect ratio of the soft magnetic material is 2-60 and the mean particle diameter (length) is 10 μm-1 mm. The electromagnetic wave absorber contains a flame retarder. The flame retarder is preferable to be an inorganic hydroxide and/or a phosphide compound. In addition, the electromagnetic wave absorber is compounded of a high strength base material or has an adhesive layer between the electromagnetic wave absorber and the high strength base material.