A state change of a person is captured with timing closer to consciousness of the person. A frequency slope waveform of a time series signal of a pulse wave of a body of a person detected by an air pack is obtained by a frequency slope time-series analyzing and computing means 612 and a frequency fluctuation time-series waveform is obtained by a frequency fluctuation time-series analyzing and computing means 613. By comparing changes of two waveforms with each other in a waveform determining means 614, a state change of a person can be captured with timing closer to consciousness of the person. A sleep-onset point can be specified clearly based upon the case where a fluctuation waveform steep gradient portion indicating a steep gradient change emerges in the frequency fluctuation waveform, and amplitude and a base line position of the frequency fluctuation waveform or the frequency slope waveform are in predetermined ranges. Further, when a mean slope line of the fluctuation waveform steep gradient portion is approximately parallel to a mean slope line of the slope waveform steep gradient portion in the frequency slope waveform before emergence of the fluctuation waveform steep gradient portion, a sleepiness waveform is determined, so that a sleepiness state leading to sleep onset can be detected.
