||Anesthesia is an unique condition for human body. Anesthesiologist administers anesthetics based on physiologic information,such as heart rate, blood pressure and electroencephalography(EEG), as these physiologic information reflects inner dynamics of human body. My study interest started from an obscure phenomenon: the instantaneous heart rate became regularly oscillatory in deeper level of anesthesia, whereas it became less regularly in lighter level. I proposed a model that simultaneously satisfies the up-to-date understandings of anesthesiology, neurology, and mathematics. Then, I developed a new quantification method to provide practical information about the anesthetic depth.