An antenna of a communication device includes a metal frame, a metal back cover and a printed circuit board. The printed circuit board includes a first circuit block and a second circuit block electrically connected to the first circuit block. A first conductor is connected between a first part of the metal frame and a signal terminal of the first circuit block. A second conductor is connected between a second part of the metal frame and a ground terminal of the first circuit block. A third conductor is connected to a third part of the metal frame. A fourth conductor is connected to a ground terminal of the second circuit block, and at least one coupling gap is defined between the third conductor and the fourth conductor. A signal terminal of the second circuit block is electrically connected to a fourth part of the metal frame.