Operations of a building facility monitoring device and an IP network monitoring device are coordinated with each other. In a connection system of a building facility device managing system, when a status of the IP network monitoring device is changed, a monitoring-device-status managing unit 301 provides parameter information unique for a BACnet protocol to the changed status and stores it. If the status is not an operation command, a coordinated-packet-generation transmitting/receiving unit 302 generates a packet of the BACnet protocol based on a status and parameter information of a specific IP network monitoring device to transmit it to a building facility device managing system 103. If the status is the operation command, it acquires a status and parameter information of the specific IP network monitoring device from a management database 401, and generates a packet of the BACnet protocol based on the status and the parameter information to transmit it to the building facility device managing system 103.