A relay device (111 1 ) to which a unique relaying channel is allocated, the relay device (111 1 ) comprising: a memory unit which stores identification information of a plurality of wireless communication terminal devices (TA - TD) registered beforehand in the own relay device (111 1 ) and identification information of a plurality of wireless communication terminal devices (TE, TF) registered beforehand in at least another relay device (111 2 ) that is different from the own relay device (111 1 ); a bus interface which provides mutually communication via a communication line with the other relay device (111 1 ); a controller which performs control to transmit, with use of the unique relaying channel, control information to the plurality of wireless communication terminal devices (TA - TH) stored in the memory unit and to relay, with use of the unique relaying channel, communication between the plurality of wireless communication terminal devices (TA - TD) registered in the own relay device (111 1 ) or communication between the plurality of wireless communication terminal devices (TE, TF) registered on the other relay device (111 2 ), wherein the controller transmits, from the bus interface to the other relay device (111 2 ), own-device information containing channel information indicating whether the unique relaying channel of the own relay device (111 1 ) is in a busy or idle state, and receives, from the other relay device (111 2 ), respective own-device information of the other relay device (111 2 ) via the bus interface , and when the own-device information of the other relay device (111 2 ) is not received from the other relay device (111 2 ), functions as the other relay device (111 2 ) by transmitting control information to the plurality of wireless communication terminal devices (TA - TD) registered in the own relay device (111 1 ) and to the plurality of wireless communication terminal devices (TE, TF) registered in the other relay device (111 2 ). a memory unit which stores identification information of a plurality of wireless communication terminal devices (TA - TD) registered beforehand in the own relay device (111 1 ) and identification information of a plurality of wireless communication terminal devices (TE, TF) registered beforehand in at least another relay device (111 2 ) that is different from the own relay device (111 1 ); a bus interface which provides mutually communication via a communication line with the other relay device (111 1 ); a controller which performs control to transmit, with use of the unique relaying channel, control information to the plurality of wireless communication terminal devices (TA - TH) stored in the memory unit and to relay, with use of the unique relaying channel, communication between the plurality of wireless communication terminal devices (TA - TD) registered in the own relay device (111 1 ) or communication between the plurality of wireless communication terminal devices (TE, TF) registered on the other relay device (111 2 ), wherein the controller transmits, from the bus interface to the other relay device (111 2 ), own-device information containing channel information indicating whether the unique relaying channel of the own relay device (111 1 ) is in a busy or idle state, and receives, from the other relay device (111 2 ), respective own-device information of the other relay device (111 2 ) via the bus interface , and when the own-device information of the other relay device (111 2 ) is not received from the other relay device (111 2 ), functions as the other relay device (111 2 ) by transmitting control information to the plurality of wireless communication terminal devices (TA - TD) registered in the own relay device (111 1 ) and to the plurality of wireless communication terminal devices (TE, TF) registered in the other relay device (111 2 ). <EOS>