Provided is a sheet-form electromagnetic wave absorber which has excellent electromagnetic absorption performance in millimeter-wave-band frequencies, and which is light, and has excellent flexibility. Provided are: a millimeter-wave-band electromagnetic wave absorption sheet that is provided with an electromagnetic wave reflection layer (A), an electromagnetic wave absorption lower layer (B) placed in parallel to the top part of the electromagnetic wave reflection layer (A), and an electromagnetic wave absorption upper layer (C) placed in parallel to the top part of the electromagnetic wave absorption lower layer (B), wherein the real number part of the dielectric constant at frequency 79 GHz of the electromagnetic wave absorption lower layer (B) is within the range of 5-45, the absolute value of the imaginary number part is within the range of 0.5-15, the film thickness of the electromagnetic wave absorption lower layer (B) is within the range of 0.10-1.5 mm, the real number part of the dielectric constant at frequency 79 GHz of the electromagnetic wave reflection upper layer (C) is 2-20, the absolute value of the imaginary number part is less than 2, and the film thickness of the electromagnetic wave reflection upper layer (C) is within the range of 0.3-2.2 mm; a millimeter-wave-band electromagnetic wave absorption method in which said electromagnetic wave absorption sheet is used; and a method for preventing electromagnetic wave disturbance.
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