A mobile device includes a ground element, a first radiation element, a second radiation element, a matching circuit, and a first metal frame. The first radiation element is coupled to a first grounding point on the ground element. The second radiation element is coupled through the matching circuit to a second grounding point on the ground element. A first coupling gap is formed between the second radiation element and the first radiation element. The first metal frame is coupled to a connection point on the first radiation element. A second coupling gap is formed between the second radiation element and the first metal frame. An antenna structure is formed by the first radiation element, the second radiation element, the matching circuit, and the first metal frame. A signal source is coupled to a feeding point on the first radiation element, so as to excite the antenna structure.