1. A case image registration apparatus comprising: a determination unit which compares case information corresponding to an object image, which is a case image to be determined whether registration to a database is required or not, and an amount of feature of the object image, with case information corresponding to a registered image, which is a case image other than the object image and has been registered in the database, and an amount of feature of the registered image, and determines whether to register the object image in the database or not according to a result of the comparison; and a registration unit which registers the object image when the determination unit determines to register the object image in the database.