A mobile device includes a metal mechanism element, a feeding radiation element, a first radiation element, a second radiation element, and a dielectric substrate. The metal mechanism element has a slot. The slot has an open end and a closed end. The feeding radiation element has a feeding point. The first radiation element extends across the slot of the metal mechanism element. The feeding radiation element is coupled through the first radiation element to a ground voltage. The second radiation element is coupled to the feeding radiation element. The dielectric substrate is adjacent to the metal mechanism element. The feeding radiation element, the first radiation element, and the second radiation element are disposed on the dielectric substrate. An antenna structure is formed by the feeding radiation element, the first radiation element, the second radiation element, and the slot of the metal mechanism element.