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).