There is provided one exemplary array antenna system having a plurality of arrayed element antennas and transmit/receive modules that are respectively connected with those element antennas and that apply a predetermined phase shift amount to transmitting signals to be supplied to the element antennas and to received signals received by the element antennas, wherein the transmit/receive module has one transmitting path that is connected to first and second element antennas and that amplifies and distributes the transmitting signal to the first and second element antennas after applying a predetermined transmitting phase shift amount and two receiving paths that amplify and apply respectively a receiving phase shift amount to the received signals received from the first and second element antennas.