An antenna comprises a first transmission element, a second transmission element, a conductive element, a ground element, a ground line and a signal line. The conductive element is connected to the ground element. The first transmission element is connected to the conductive element. The first transmission element comprises a first spiral structure and a first axis. The second transmission element is connected to the conductive element. The ground line is electrically connected to the ground element. The signal line is electrically connected to the conductive element at a feed point.