An antenna module connected to a system ground of an electronic device includes a substrate, a coaxial-transmission line, a first radiator and a second radiator. The coaxial-transmission line includes a power feed-in terminal and a ground terminal. The first radiator is electrically connected to the power feed-in terminal. The second radiator is electrically connected to the ground terminal. One side of the second radiator is connected to the system ground, and the second radiator includes a first terminal and a second terminal. An opening is formed between the first terminal and the second terminal, so that the second radiator be partially surrounding to the first radiator. The first radiator and the second radiator are coplanarly disposed on the substrate.