An antenna structure includes a loop radiation element, a balance radiation element, a first additional radiation element, and a second additional radiation element. The loop radiation element has a first feeding point. The balance radiation element has a second feeding point. The balance radiation element is coupled to at least a first connection point on the loop radiation element. The balance radiation element is substantially surrounded by the loop radiation element. The first additional radiation element is coupled to a second connection point on the loop radiation element. The second additional radiation element is coupled to a third connection point on the loop radiation element. The loop radiation element is disposed between the first additional radiation element and the second additional radiation element.