PURPOSE: To unitedly manage independent management systems by assigning a global ID being identification information of the same system to all sub management systems.

CONSTITUTION: A table converting a local ID and a global ID mutually is prepared by a united management equipment, the table is sent to a packet network management equipment 112, a PBX network management equipment 122 and an LAN management equipment 132, in which the table is stored as conversion tables 113, 123 and 133 respectively. When a network management equipment 160 requests a management data relating to a PBX 121 of a PBX system 120, the equipment 160 sends a global ID and a command to the PBX network management equipment 122. The PBX network management equipment 122 converts the received global ID into a corresponding local ID by using the conversion table 123 and requests the management data to the PBX 121.