Abstract: The invention provides a millimeter wave radar monitoring system, which can reduce the installation cost and can improve reliability with less probability of false alarms. A millimeter wave radar unit includes a millimeter wave radar having a transmitting antenna for radiating a radio wave and a receiving antenna for receiving a wave reflected by a target having received the radio wave radiated from the transmitting antenna, and includes a signal processing unit for the received radio wave. A target tracking and monitoring circuit section in a monitoring unit collates position information of the target detected by the millimeter wave radar unit with monitoring area layout information held in a monitoring area layout signal section, thereby tracking a motion of the target. The target is displayed on a display along with the monitoring area layout information. When it is determined that the target is a suspicious invader, a warning device issues an alarm.