A monitoring control system including a monitoring device to monitor communication data communicated between communication terminals via a communication infrastructure. The monitoring device includes an address conversion table for storing a transmission source address and a transfer destination address in a corresponding relationship; a transfer unit receiving the communication data, obtaining a transfer destination address corresponding to a transmission source address of the received communication data from the address conversion table, and transferring the received communication data based on the obtained transfer destination address; and monitoring unit monitoring the received communication data.