A device to detect a state of a human being is provided. The device determines 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 determines time-series waveforms of a frequency slope and 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, and then determines a state of the human being from a time-series change in each power spectrum. Dominant degrees of the functional adjustment signal and activity adjustment signal are compared as distribution rates thereof, in addition to a degree of progress of fatigue, to determine a state of the human being, for example a relaxed state, fatigued state, prominent state of sympathetic nervous, prominent state of parasympathetic nervous.
