A vehicle antenna includes a first Automatic Gain Control (AGC) unit and a second AGC unit. The first AGC unit may attenuate an input signal based on the strength of the input signal, and then output the attenuated signal to a transistor. The second AGC unit may control a power to be supplied or not to the transistor using a switching function based on the strength of the input signal. With the antenna, the signals of a strong electric field as well as the signals of a weak electric field adjacent to the strong electric field can be effectively controlled.