To avoid nonconformities of mis-operations of an alarm from becoming wrong recognition of shoplifting by narrowing the detection range in which the alarm operates to the minimum limit required, and enlarge an effective using area of a sales floor by sufficiently ensuring a commodity display place.

In the shoplifting prevention device, an existence of an object to be detected can be detected within a management area set by a transmission antenna for transmitting a radio wave and a receiving antenna for receiving the above radio wave. A detection area, where an alarm is operated by a plurality of human body sensors, is provided in the above management area.