A monitoring device comprising: a) a background information storage unit configured to store first and second background information related to positional information of a fixed object existing in a detection area of a radar device that receives a reflected wave from an object existing at an emission destination of an emitted radar wave and detects position and moving velocity information of the object as detection information of the object; and b) a detection unit configured to detect, a monitoring object existing in a detection area of the radar device by using the detection information detected by the radar device and the first or second background information stored in the background information storage unit, wherein the detection unit includes: b1) a first detection unit configured to detect, upon receiving a first specified signal from a higher level device, a temporary fixed object existing in a detection area of the radar device by using the detection information detected by the radar device and the first background information about an object that has remained at rest for a long time in the detection area, which is stored in the background information storage unit and to output a detection result to the higher level device; and b2) a second detection unit configured to detect, upon receiving a second specified signal from the higher level device, a movement object existing in the detection area of the radar device by using the detection information detected by the radar device and the second background information about an object that recently stopped moving in the detection area, which is stored in the background information storage unit, and to output a detection result to the higher level device. a) a background information storage unit configured to store first and second background information related to positional information of a fixed object existing in a detection area of a radar device that receives a reflected wave from an object existing at an emission destination of an emitted radar wave and detects position and moving velocity information of the object as detection information of the object; and b) a detection unit configured to detect, a monitoring object existing in a detection area of the radar device by using the detection information detected by the radar device and the first or second background information stored in the background information storage unit, wherein the detection unit includes: b1) a first detection unit configured to detect, upon receiving a first specified signal from a higher level device, a temporary fixed object existing in a detection area of the radar device by using the detection information detected by the radar device and the first background information about an object that has remained at rest for a long time in the detection area, which is stored in the background information storage unit and to output a detection result to the higher level device; and b2) a second detection unit configured to detect, upon receiving a second specified signal from the higher level device, a movement object existing in the detection area of the radar device by using the detection information detected by the radar device and the second background information about an object that recently stopped moving in the detection area, which is stored in the background information storage unit, and to output a detection result to the higher level device. b1) a first detection unit configured to detect, upon receiving a first specified signal from a higher level device, a temporary fixed object existing in a detection area of the radar device by using the detection information detected by the radar device and the first background information about an object that has remained at rest for a long time in the detection area, which is stored in the background information storage unit and to output a detection result to the higher level device; and b2) a second detection unit configured to detect, upon receiving a second specified signal from the higher level device, a movement object existing in the detection area of the radar device by using the detection information detected by the radar device and the second background information about an object that recently stopped moving in the detection area, which is stored in the background information storage unit, and to output a detection result to the higher level device.