A millimeter wave antenna apparatus for an electronic device includes a rear housing and at least one antenna assembly, the at least one antenna assembly includes a millimeter wave module spaced apart from the rear housing, and being configured to transceive millimeter wave signal; a beam of the millimeter wave signal pointing towards the outside of the rear housing; a dielectric layer arranged in a target area of the rear housing, the target area at least comprising an area where the millimeter wave module is projected onto the rear housing, the dielectric layer and a part of the rear housing in the target area together forming a radiation layer with gradient distribution of dielectric constant, and the radiation layer being configured to change a beam radiation direction of the millimeter wave signal.