To provide a maintenance system and its method for an NC(numeric control) machine tool which realizes the manpower saving and quickening of maintenance service by utilizing a network function of a personal computer part.

When a personal computer part 20 performs web connection between a server device 30 and itself and it transmits the ID number of an NC machine tool 1 to the server device 30, the device 30 distributes an alarm decision module. When a web browser of the part 20 executes the alarm decision module and transmits an alarm number, etc., to the device 30, the device 30 distributes a corresponding alarm questionaire module. The web browser executes the alarm questionaire module, shows the questionaire list corresponding to the alarm number on a screen and displays advice for normally recovering a part working unit 9 based on operator's check.