To provide a system and a method for machine-tool maintenance which enable administrators of machine tools to easily unify and use the machine tools without being aware of their makers, machine types, etc.

A monitor device 20 sends sensor information obtained from an NC machine tool 50 to a network server 40 at arbitrary intervals and also sends emergency alarm information to the network server 40 once obtaining it from the NC machine tool 50. The network server 40 notifies the NC machine tool administrators of the operation states of the NC machine tools 50 (the value of some sensor exceeds a sensor threshold or the emergency alarm information is present) by performing notifying operations (notifying method) defined as class objects by NC machine tools 50 by using the sent sensor information and emergency alarm information, i.e., according to instances generated from the class objects.