To use an EMI washer repeatedly, improve workability and shield a high frequency surely by composing the washer of a washer-shaped metallic thin plate of spring property and conductive rubber formed integratedly in the inside thereof.

In the case where a cover 5 is installed on a main body 6, a washer is installed between a screw head 4 and a cover 5 in the same way as that a normal washer is used, in order to obtain the high frequency shield formed around the screw head. When the screw head 4 is rotated and a screw is fastened, a conductive rubber 3 is sagged between the screw head 3 and the cover 5 firstly, a bending part 2 is brought in contact with the screw head 4, and the outer peripheral part of a metal thin plate 1 is brought in contact with the cover 5. The metal thin plate 1, the bending part 2, and the conductive rubber 3 are sagged so as to be brought in contact with the screw head 4 and the cover 5 surely, and thereby, high frequency shield is ensured. Since the metal thin plate 1 having rubber and spring property is used, a device is used repeatedly. Since the device is formed in a washer shape, it is removably installed in the same way as normal screw fastening work so as to improve workability.