Feature values calculated from a peripheral image area of feature points extracted in a detection target object in a training image each are labeled with a label indicating a class of the detection target object, feature values calculated from a peripheral image area of feature points of a non detection target object in the training image each are labeled with a label indicating the non detection target object, voting positions in a parameter space are calculated by relative positions of the feature points of the detection target object from the detection target object on the training image, and a first classifier is learned using the labeled feature values extracted in the training image so that a class distribution is concentrated and the voting positions in the parameter space are concentrated.