an image monitoring system may include an object area detection processing section and an object area tracking processing section . the object area detection processing section may be configured to detect object area information from an image obtained by an input image signal on a basis of the input image signal . the object area tracking processing section may be configured to perform object area tracking processing by associating a current object area with a past object area on a basis of the object area information detected by the object area detection processing section . the object area tracking processing section may associate the current object area with the past object area using unique identifying information . the object area tracking processing section may continue to retain identifying information given to a predetermined object area that has disappeared , and may give the retained identifying information to the predetermined object area when the predetermined object area reappears .