1. A subject state discriminating method, comprising the steps of: preparing a plurality of types of state classifiers, for judging whether a judgment target image includes a predetermined subject in predetermined states, each type of state classifier corresponding to each of the predetermined states; obtaining a single image from among a plurality of temporal series images of the predetermined subject; applying at least one of the types of state classifiers to the obtained image to judge whether the obtained image includes the predetermined subject; and discriminating that the predetermined subject within the obtained image is in a state corresponding to that of the state classifier that judged that the predetermined subject is included in the obtained image, in the case that any of the state classifiers judges that the predetermined subject is included in the obtained image; wherein: stepwise changes in the state of the predetermined subject are obtained, based on previously discriminated states of the predetermined subject within a plurality of temporal series images preceding the obtained image; at least one state of the predetermined subject is predicted for the obtained image, based on the stepwise changes; and the state classifier that corresponds to the at least one predicted state is prioritized over other state classifiers, when applying the state classifiers to the obtained image.