An antenna device includes an insulating substrate, a ground plane, a radiating element, a horizontal feed probe and a vertical feed probe. The insulating substrate has a first surface and a second surface opposite to the first surface. One end of the first surface defines an insulating area. One end of the second surface adjacent to the insulating area defines a first isolating area, a second isolating area, a horizontal feed circuit and a vertical feed circuit. The ground plane includes a first ground plane and a second ground plane. The radiating element is located onto the insulating area. The horizontal and vertical feed probes are inserted in the insulating substrate and the radiating element with one end thereof projecting beyond the radiating element and the other end thereof respectively penetrating through the first and second isolating areas so as to couple with the horizontal and vertical feed circuits, respectively.