PURPOSE: To allow even a person in charge of maintenance with less experience to process fault recovery quickly and surely.

CONSTITUTION: A fault message sent from a communication site of a communication network is transferred from the communication network management equipment to a computer 6 via a LAN 5, an intelligent base data section 62 of the computer 6 generates a proper diagnostic command based on a database with respect to the fault message and sends the command to a communication site being a fault message sender. Then a reply message returned from the communication site with respect to the diagnostic command is transferred to the computer 6 via the LAN 5 from the communication management equipment, an inference processing section 63 of the computer 6 collates the reply message with basic data prepared in advance and generates fault state display data based on the result of collation and transfers the data to the communication management equipment and the data are displayed on a display device.