A relay communication system in which mutually remote LANs communicate with each other via a WAN is provided with a means for preventing a plurality of call controls and a plurality of communication paths in each of a plurality of sections from crossing over one another. Relay servers (12, 22) relay communications between client terminals (11, 21). The relay servers (12, 22) create two pieces of information and cause the two pieces of information to be shared in the whole relay communication system. One of the two pieces of information is relay group information indicating that the relay servers (12, 22) constitute a relay group. The other is relay server information indicating the client terminals (11, 21) that can communicate with the respective relay servers (12, 22). Each of the relay servers (12, 22) and client terminals (11, 21) checks information, which identifies a call control transmitted to the other end of communication in each section when the call control is executed, against information that identifies a call control received from the other end of communication in each section when a communication path is established, thereby associating the call control with the communication path in each section.