Provided is a technique for more accurately assessing the state of a living body. Using a predetermined central-nervous-system index value calculated from central-nervous-system living-body signal information and a predetermined peripheral-system index value calculated from peripheral-system living-body signal information, the present invention estimates the state of the living body from the positional relationship between coordinate points on a coordinate system in which the predetermined central-nervous-system index value and the predetermined peripheral-system index value are plotted on coordinate axes. When the state of a person is to be estimated, by adopting a configuration in which both indexes are used rather than one or the other and the indexes are determined on a single coordinate system, as in the present invention, fluctuations in each index relative to variations in the state of the person are emphasized, and the state of the person can be more accurately estimated.
