A biological body state estimation device which can capture not only activities of autonomous nerves but also an activated state of a brain function is provided. The biological body state estimation device is configured such that a homeostatic function level is sorted and acquired in a plurality of stages by using a biological signal obtained from the upper body of a person and each stage of the homeostatic function level is plotted in a time series in accordance with a time axis indicated on the lateral axis and displayed as a graph by display means. It is preferable that the highest part on the vertical axis of the graph is displayed as a highly active state and the lowest part as a function decline state. As a result, a state of fluctuation due to the autonomous nerves as an attempt to maintain homeostasis, progress of a feeling of fatigue, and a state stimulated by activation of the brain can be captured as a periodic function. Moreover, a sleep prediction phenomenon can be also captured.
