1. An image processing apparatus, comprising: an edge detection processing section configured to generate an edge image by performing edge detection processing on a detection target image from which a target object is to be detected; a segment area setting section configured to segmentalize the edge image into a plurality of segment areas; an index value calculation section configured to calculate, for each of the plurality of segment areas, an edge component index value that indicates an amount of edge components included in each segment area; and a target object determining section configured to determine whether there is an image of the target object in each segment area based on the edge component index value.