A surveillance system comprising: a surveillance region storage means storing a surveillance region that is a partial region within an image pickup region signifying a region desired to be surveilled, the surveillance region is set by selecting a location or a range within the image pickup region; and an image analyzing means arranged a) to determine whether or not at least a portion of an object in an input image is located within the surveillance region stored in the surveillance region storage means, and if the object is not located within the surveillance region, the object is excluded from being a subject desired to be detected; and, b) if it was determined according to a) that at least a portion of the object is located within the surveillance region, to determine whether or not the object meets a predetermined condition; and an effective region storage means that stores a region, which is a predetermined region within the image pickup region and partially overlaps with the surveillance region, as an effective region, the effective region signifies a region in which just the object that is included within its range is detected as a detection subject; wherein the image analyzing means determines, as the predetermined condition, whether or not the object is included within the range of the effective region stored in the effective region storage means, wherein the effective region has a region that is not overlapped with the surveillance region, wherein the effective region in the image pickup region is predetermined based on the detection subject that is expected to fit in, and wherein, if the object that does not fit within the range of the effective region, the object is excluded from being the detection subject. a surveillance region storage means storing a surveillance region that is a partial region within an image pickup region signifying a region desired to be surveilled, the surveillance region is set by selecting a location or a range within the image pickup region; and an image analyzing means arranged a) to determine whether or not at least a portion of an object in an input image is located within the surveillance region stored in the surveillance region storage means, and if the object is not located within the surveillance region, the object is excluded from being a subject desired to be detected; and, b) if it was determined according to a) that at least a portion of the object is located within the surveillance region, to determine whether or not the object meets a predetermined condition; and a) to determine whether or not at least a portion of an object in an input image is located within the surveillance region stored in the surveillance region storage means, and if the object is not located within the surveillance region, the object is excluded from being a subject desired to be detected; and, b) if it was determined according to a) that at least a portion of the object is located within the surveillance region, to determine whether or not the object meets a predetermined condition; and an effective region storage means that stores a region, which is a predetermined region within the image pickup region and partially overlaps with the surveillance region, as an effective region, the effective region signifies a region in which just the object that is included within its range is detected as a detection subject; wherein the image analyzing means determines, as the predetermined condition, whether or not the object is included within the range of the effective region stored in the effective region storage means, wherein the effective region has a region that is not overlapped with the surveillance region, wherein the effective region in the image pickup region is predetermined based on the detection subject that is expected to fit in, and wherein, if the object that does not fit within the range of the effective region, the object is excluded from being the detection subject.