A wireless communication system comprising: a relay system comprising a plurality of relay devices (111 1 to 111 n), which are arranged in the same communication area for bearing a relaying process, which are connected one another via a communication line and to which unique channels are respectively allocated; and a plurality of wireless terminal devices (TA to TH) which are adapted to communicate with each other via the relay system, wherein each relay device (111 1 to 111 n) is adapted to transmit control information to the wireless terminal device (TA to TH) which is registered in said relay device (111 1 to 111 n), each wireless terminal device (TA to TH) is adapted to receive the control information transmitted from the relay device (111 1 to 111 n) which registers the own wireless terminal device (TA to TH), selects a channel which is currently able to relay a communication among the channels respectively allocated to the relay devices (111 1 to 111 n) based on the received control information, and is adapted to communicate with another wireless terminal device (TA to TH) via the selected channel, and each relay device (111 1 to 111 n) is adapted to exchange a communication signal via the communication line to exchange information configuring the control information, and synchronize a downlink signal which is wirelessly transmitted by said relay device (111 1 to 111 n) with the communication signal transmitted over the communication line, and each wireless terminal device (TA to TH) maintains, when shifting a channel for communication to another channel, a synchronized state established in a channel prior to shifting for at least a predetermined period. a relay system comprising a plurality of relay devices (111 1 to 111 n), which are arranged in the same communication area for bearing a relaying process, which are connected one another via a communication line and to which unique channels are respectively allocated; and a plurality of wireless terminal devices (TA to TH) which are adapted to communicate with each other via the relay system, wherein each relay device (111 1 to 111 n) is adapted to transmit control information to the wireless terminal device (TA to TH) which is registered in said relay device (111 1 to 111 n), each wireless terminal device (TA to TH) is adapted to receive the control information transmitted from the relay device (111 1 to 111 n) which registers the own wireless terminal device (TA to TH), selects a channel which is currently able to relay a communication among the channels respectively allocated to the relay devices (111 1 to 111 n) based on the received control information, and is adapted to communicate with another wireless terminal device (TA to TH) via the selected channel, and each relay device (111 1 to 111 n) is adapted to exchange a communication signal via the communication line to exchange information configuring the control information, and synchronize a downlink signal which is wirelessly transmitted by said relay device (111 1 to 111 n) with the communication signal transmitted over the communication line, and each wireless terminal device (TA to TH) maintains, when shifting a channel for communication to another channel, a synchronized state established in a channel prior to shifting for at least a predetermined period.