An electromagnetic shielding device is used for shielding an electromagnetic wave and comprises a supporting part and a cover plate; the supporting part is a hollow framework provided with openings at the two ends thereof and enclosed by a plurality of side walls connected in sequence; a gap is formed on one of the side walls; and the cover plate is used for being inserted in the supporting part from the gap, so as to shield the opening at one end of the supporting part. Because the cover plate is inserted in the supporting plate from the gap on one of the side walls, when an electronic element on a circuit board fails to function, an engineer can pull the cover plate out of the supporting part for viewing. Therefore, the electromagnetic shielding device is conveniently operated by the engineer.