An object detection apparatus for detecting a target object in an input image. The apparatus includes a storage storing, for each of a plurality of part areas forming an area subject to image recognition processing, image recognition dictionaries used to recognize a target object and typed according to variations in appearance of a part of the target object to be detected in the part area. A part score calculator calculates, for each of the part areas, a part score indicative of a degree of similarity between the part area and each of at least some of the image recognition dictionaries. An integrated score calculator calculates an integrated score that is a weighted sum of the part scores for the respective part areas. A determiner determines, on the basis of the integrated score, whether or not the target object is present in the subject area.