A communication system comprising: a plurality of communication devices (4-1 to 4-8) connected so as to be able to mutually communicate and to constitute a network; each of the plurality of communication devices (4-1 to 4-8) comprising: a first wireless communication section functioning as a wireless relay device of the network: and a second wireless communication section functioning as a slave unit to be connected to another communication device (4-1 to 4-8) in the network, wherein: the second wireless communication section of a lower-level communication device (4-1 to 4-8) is configured to access the first wireless communication section of a higher-level communication device (4-1 to 4-8), whereby the higher-level communication device (4-1 to 4-8) and the lower-level communication device (4-1 to 4-8) are connected so as to constitute the network, each of the plurality of communication devices (4-1 to 4-8) stores system information including connection information for connection to the first wireless communication section of each of the plurality of communication devices (4-1 to 4-8) constituting the network, when any one of the plurality of communication devices (4-1 to 4-8) is disconnected from the higher-level communication device (4-1 to 4-8) being connected thereto, the disconnected communication device (4-1 to 4-8) is configured to search for another communication device (4-1 to 4-8) constituting the network using the system information and to make reconnection to the communication device (4-1 to 4-8) detected by the search, and the first wireless communication section is configured to operate as a wireless relay device in a stealth mode, and the disconnected communication device (4-1 to 4-8) is configured to search for the other communication device (4-1 to 4-8) by active scanning using the connection information obtained from the system information; characterized in that the system information is updated periodically in the network, and the disconnected communication device (4-1 to 4-8) is configured to: make temporary connection to one of the plurality of communication devices (4-1 to 4-8) based on the system information having been stored at the time of the disconnection, obtain the updated system information from the communication device (4-1 to 4-8) used for the temporary connection, determine a communication device (4-1 to 4-8) for regular connection based on the obtained system information, and make regular connection to the determined communication device (4-1 to 4-8). a plurality of communication devices (4-1 to 4-8) connected so as to be able to mutually communicate and to constitute a network; each of the plurality of communication devices (4-1 to 4-8) comprising: a first wireless communication section functioning as a wireless relay device of the network: and a second wireless communication section functioning as a slave unit to be connected to another communication device (4-1 to 4-8) in the network, wherein: a first wireless communication section functioning as a wireless relay device of the network: and a second wireless communication section functioning as a slave unit to be connected to another communication device (4-1 to 4-8) in the network, wherein: the second wireless communication section of a lower-level communication device (4-1 to 4-8) is configured to access the first wireless communication section of a higher-level communication device (4-1 to 4-8), whereby the higher-level communication device (4-1 to 4-8) and the lower-level communication device (4-1 to 4-8) are connected so as to constitute the network, each of the plurality of communication devices (4-1 to 4-8) stores system information including connection information for connection to the first wireless communication section of each of the plurality of communication devices (4-1 to 4-8) constituting the network, when any one of the plurality of communication devices (4-1 to 4-8) is disconnected from the higher-level communication device (4-1 to 4-8) being connected thereto, the disconnected communication device (4-1 to 4-8) is configured to search for another communication device (4-1 to 4-8) constituting the network using the system information and to make reconnection to the communication device (4-1 to 4-8) detected by the search, and the system information is updated periodically in the network, and the disconnected communication device (4-1 to 4-8) is configured to: make temporary connection to one of the plurality of communication devices (4-1 to 4-8) based on the system information having been stored at the time of the disconnection, obtain the updated system information from the communication device (4-1 to 4-8) used for the temporary connection, determine a communication device (4-1 to 4-8) for regular connection based on the obtained system information, and make regular connection to the determined communication device (4-1 to 4-8). make temporary connection to one of the plurality of communication devices (4-1 to 4-8) based on the system information having been stored at the time of the disconnection, obtain the updated system information from the communication device (4-1 to 4-8) used for the temporary connection, determine a communication device (4-1 to 4-8) for regular connection based on the obtained system information, and make regular connection to the determined communication device (4-1 to 4-8).