The invention relates to an electromagnetic shielding device that can be used for microwave ovens and computers, in particular to an electromagnetic shielding device that is provided with negative permeability material and used for microwave ovens and computers. Photonic bandgap effect of the negative permeability material can be used for restraining electromagnetic radiation leakage. The invention is mainly characterized in that the shielding device is made of metal material and is provided with split ring resonators (SRRs) of certain thickness and proper geometry size. The holes and hollows on the prior shielding box body are replaced by the SRRs, and the electromagnetic radiation leakage of the holes and the hollows can be restrained. The thickness of the split ring resonators of the invention is ranged from 0.6 mm to 1.5 mm, and other geometric parameters are controlled by the central operating frequency of the equipment and the instrument. The invention has the advantages of simple and easy operation, no effect on the normal operation of the equipment and no need to alter the design of the electrical apparatus and the electronic equipment. Not only the functions of heat dissipation, air exhaust and the like of the prior holes and hollows remain, but also the electromagnetic radiation leakage is restrained.