Abstract: A wideband millimeter-wave antenna device includes an antenna radiation layer and a transparent metasurface layer. The antenna radiation layer is below a transparent panel of a display panel and maintains a spaced height from the transparent panel. The transparent metasurface layer is on an upper surface of the transparent panel. The antenna radiation layer includes a dielectric substrate, a radiating metal portion, and a ground plane. The dielectric substrate is below the transparent panel and includes a first surface and a second surface, and the first surface faces the transparent panel. The radiating metal portion is on the first surface. The ground plane is on the second surface. The transparent metasurface layer includes a transparent substrate and metasurface units. The transparent substrate is on the upper surface of the transparent panel. The metasurface units are on the transparent substrate. Each metasurface unit is formed by a diamond-grid metal wire.