PURPOSE: To easily and surely perform network management by automatically attaching a network address on a client device from which the network address is requested by address managing service.

CONSTITUTION: An address managing server 10 stores the range of the network address to be attached on the client device, a host device name, and the network address in its own device as a pair of tables. The server 10 registers a new network address on the table of its own device when the attachment of the network address is requested from the client devices 12a-12e. Following that, the network address is notified to and attached on the devices 12a-12e from which a request is issued via a LAN transmission line 14. Thereby, the network address can automatically be attached.