MONITORING DEVICE

An image monitoring system includes: a reference image generation unit generating a reference image serving as a reference image, based on an input image; a foreground extraction unit detecting, from the input image, a foreground region different from the reference image; a stationary region extraction unit extracting a stationary region from the foreground region; a feature quantity extraction unit extracting a feature quantity of the stationary region; a feature quantity recording unit recording feature quantities as a function of time; a stationary object detection unit clustering pixels, recorded feature quantities of which meet predetermined criteria, and detecting a stationary object; a left object determination unit determining whether the stationary object is a left object, based on a feature quantity of the stationary object and evaluation of the surrounding environment; and a left object management unit managing attributes of left objects, and issuing a report when a certain condition is met.