A system providing greatly improved monitoring against wrong or fraudulent acts. A game facility monitoring system includes game machines or game-related devices provided with detectors that detect the state of a device and the operation of the device resulting from wrong or fraudulent acts, detects the state of the device and the operation of the device possibly resulting from wrong or fraudulent acts, and gives out a notification. The system may also include an anomaly warning unit that operates, when any of the detectors is triggered, a warning operation determined by an anomaly level corresponding to the detected contents of multiple anomaly levels.