An antenna structure has a first resonance mode and a second resonance mode. The antenna structure consists of a first radiation element, a second radiation element, a grounding element, and a signal feeding element. The first radiation element resonates at a first operating frequency band corresponding to the first resonance mode. The second radiation element is extended from a first end of the first radiation element and resonates at a second operating frequency band corresponding to the second resonance mode. The grounding element is extended from a second end of the first radiation element. The signal feeding element is disposed between the first radiation element and the grounding element. The second radiation element, the first radiation element, and the grounding element are formed by bending a slender metal sheet.