1. An image processing apparatus comprising: extracted information image generation means for generating a plurality of extracted information images having mutually different resolutions on the basis of the extracted information images made up of predetermined information extracted from respective areas of an input image; difference image generation means for generating a difference image by obtaining a difference between two predetermined extracted information images among the plurality of the extracted information images; information map creation means for creating an information map indicating feature quantities of features possessed by an area of a subject in the input image by performing weight addition of the plurality of difference images; normalization means for normalizing the information map by subtracting an average value of values of the respective areas of the information map from the value of each area of the information map; and subject map creation means for creating a subject map indicating the likelihood of an area being a subject in each area of the input image by performing weight addition of the plurality of normalized information maps.