A sleep state measuring apparatus includes an autonomic nerve index obtaining unit that obtains a user's autonomic nerve index; and a sleep periodicity index calculating unit that calculates a sleep periodicity index based on a temporal change of the autonomic nerve index and a change in a user's sleeping cycle, wherein the sleep periodicity index indicates whether the user is sleeping or not according to a user's ideal sleeping cycle as an index, or a dominance index calculating unit that calculates a parasympathetic nerve dominance index which shows dominance of a parasympathetic nerve index included in the autonomic nerve index with respect to a sympathetic nerve index included in the autonomic nerve index for a user during sleep.
Apparatus, method and system of measuring sleep state