A control network management system for relaying first and second wireless communications comprises a first repeater having a packet control means for writing priority information in a header of communication packet data of the first wireless communication, as received and transmitting the communication packet data with a hash value of the header, added thereto, a second repeater having a packet control means for zero-clearing priority information in a header of communication packet data of the second wireless communication, as received, or changing the priority information to a predetermined value before transmitting the communication packet data with a hash value of the header, added thereto, and a third repeater having a priority control means for applying priority control to the header of the communication packet data received from the first repeater or the second repeater, on the basis of priority information, thereby transmitting the communication packet data to a control system.