A technique for grasping a state of a human being more precisely is provided. The technique has means for determining a time-series waveform of a frequency from a time-series waveform of a biological signal acquired from an upper body of a human being, and further for determining time-series waveforms of a frequency slope and a frequency variation to analyze these frequencies. Upon analyzing the frequencies, it determines power spectrums of frequencies corresponding to a preset functional adjustment signal, fatigue reception signal, and activity adjustment signal. Then, it determines a state of a human being from a time-series change in each power spectrum. Since the fatigue reception signal indicates the degree of progress of fatigue in a usual active state, the dominant degrees of the functional adjustment signal and the activity adjustment signal are compared as distribution rates thereof, in addition to the degree of progress of fatigue, thereby being able to determine a state of a human being (a relaxed state, a fatigued state, a prominent state of the sympathetic nervous, a prominent state of the parasympathetic nervous, and the like) more precisely.
