The antenna apparatus has a base station installed in a first space partitioned by a wall, a radio terminal provided in a second space, and a repeater including passive antennas and installed on the wall. The repeater is constituted of a first antenna that transmits and receives signals to and from a base station, a plurality of second antennas that transmit and receive the signals to and from the radio terminal, and a transmission line that connects the first antenna with the second antenna. Further, the plurality of second antennas are installed such that planes of polarization of the second antennas are different from each other to improve transmission with the radio terminal.