A technology to grasp a state of a human being more accurately is provided. The technology is provided with means for acquiring a time-series waveform of a frequency from a time-series waveform of a biological signal sampled from the upper body of a human being and for further acquiring a time-series waveform of frequency slope and a time-series waveform of frequency fluctuation and for applying frequency analysis to them. In the frequency analysis, a power spectrum of each frequency corresponding to a functional adjustment signal, a fatigue reception signal, and an activity adjustment signal, respectively, determined in advance is acquired. Then, a state of a human being is determined from a time-series change of each power spectrum. The fatigue reception signal indicates a degree of progress of fatigue in a usual active state and thus, by comparing it with degrees of predominance of the functional adjustment signal and the activity adjustment signal as their distribution rates, a state of a human being (relaxed state, fatigued state, state in which sympathetic nerve is predominant, a state in which parasympathetic nerve is predominant and the like) can be determined more accurately.
