The fact that a movable object exits a specific area is judged with high accuracy. A first movement sensor detects the movement of the movable object in a first area. A second movement sensor detects the movement of the movable object in a second area including the first area. A time judgment unit judges whether or not a time difference from a time point when a measurement value obtained by the first movement sensor becomes a predetermined value or less to a time point when a measurement value obtained by the second movement sensor becomes the predetermined value or less is a first threshold value or more. An existence judgment unit judges that the movable object does not exist in the first area in the case where the time judgment unit has judged that the time difference is the first threshold value or more.