1. A moving body detecting apparatus comprising: image acquiring means for acquiring static images continuing in time sequence in the same monitoring range; and decision processing means for receiving a plurality of static images continuing in time sequence from said image acquiring means to make a comparison among said static images for making a decision as to whether or not a body moves from an area allowing the existence of a body (which will hereinafter be referred to as an “allowable area”), set in advance in said monitoring range, to an area inhibiting the existence of a body (which will hereinafter be referred to as an “unallowable area”), set in advance in said monitoring range.