Dual (redundant) operation support servers are used to improve the reliability of a video conferencing system and ensure the stability of communication. Switching automatically one operation support server to another enables a video conference to be smoothly continued without interruption. Multiple operation support servers are provided, each including a synchronization function which synchronizes site connection information and live camera information between the operation support servers and prevents an operation support server in a standby state from writing live camera information in a folder for each site. Each site PC 14 includes an automatic server change function which, when an operation support server 11 in service fails, switches connection from the operation support server 11 to an operation support server 12 in a standby state. When the operation support server in service fails, the operation support server in a standby state writes live camera information into a folder for each site and each site PC changes connection from the operation support server that was in service to the operation support server in a standby state.