1. A subject discriminating apparatus comprising: an image input means for receiving input of a target image, which is a target of discrimination; a first characteristic amount calculating means for calculating first characteristic amounts, which do not require normalization and are employed to discriminate a predetermined subject, from the target image; a first discriminating means for discriminating whether a candidate of the predetermined subject is included in the target image, by referring to first reference data, in which the first characteristic amounts and discrimination conditions corresponding to the first characteristic amounts are defined in advance, with the first characteristic amounts calculated from the target image; a second characteristic amount calculating means for calculating second characteristic amounts, which are normalized and employed to discriminate the predetermined subject, from the candidate of the predetermined subject in the case that the first discriminating means judges that the candidate is included in the target image; and a second discriminating means for discriminating whether the candidate is the predetermined subject, by referring to second reference data, in which the second characteristic amounts and discrimination conditions corresponding to the second characteristic amounts are defined in advance, with the normalized second characteristic amounts.