An antenna structure includes a radiation metal element, a first feeding metal element, a second feeding metal element, a metal loop, a ground metal element, a first dielectric layer, a second dielectric layer, and a via metal element. The radiation metal element has a first slot, a second slot, a third slot, and a fourth slot, which surround a first opening, a second opening, a third opening, and a fourth opening. The first feeding metal element extends into the first opening. The second feeding metal element extends into the second opening. The first dielectric layer is disposed between the radiation metal element and the metal loop. The second dielectric layer is disposed between the metal loop and the ground metal element. The via metal element couples a first connection point on the radiation metal element to a second connection point on the ground metal element.