An antenna device includes a single-loop radiating element, a radiating arm, a feeding element, and a grounding element. The single-loop radiating element is operable within a first frequency band. The radiating arm extends from the single-loop radiating element and is operable in second frequency band. The feeding element is connected to the single-loop radiating element and the radiating arm. The grounding element is connected to the single-loop radiating element.