A shielding apparatus for electromagnetic testing includes a platform, a lid forming a cavity, a driving unit, and an elastic gasket attached to a bottom of the lid around a rim adjacent the cavity. The platform is for placing an electronic device to be tested. The lid is for covering the platform to define a closed space. The driving unit is for lifting and lowering the lid. The gasket is for being compressed and filling gaps between the lid and the platform when the platform covers the lid.