A biological body state estimation device configured such that a homeostatic function level is sorted and acquired in plural stages by using a biological signal obtained from an upper body of a person and each stage of the homeostatic function level is plotted in time series in accordance with a time axis indicated on the lateral axis and displayed as a graph by a display. A highest part on the vertical axis of the graph can be displayed as a highly active state and a lowest part as a function decline state. Therefore, a state of fluctuation due to 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 captured.
