A communication device includes a ground element and an antenna element. The antenna element includes a first radiation element, a second radiation element, and a control circuit. One end of the first radiation element is coupled to a signal source, and another end of the first radiation element is an open end. The second radiation element includes at least a first portion and a second portion. A first end of the first portion is a shorted end coupled to the ground element, and a fourth end of the second portion is an open end. The second radiation element surrounds the open end of the first radiation element. The control circuit is coupled between a second end of the first portion and a third end of the second portion of the second radiation element. The control circuit provides at least two different impedances.