A communication device including an antenna structure is provided, wherein the antenna structure includes a ground element, an antenna element, and a circuit element group. The ground element has a notch at one of its edges, and a long edge of the notch is at least two times longer than a short edge of the notch. The antenna element includes a metal portion disposed in the notch. Two ends of the metal portion are extended away from each other and are positioned substantially at or around two opposite edges of the notch. One end of the metal portion is coupled to the ground element, and the other end of the metal portion is a feeding terminal of the antenna element. The circuit element group includes at least a capacitive element and an inductive element.