A peak-relevant value device acquires a peak-relevant value (for example, the peak value of an R wave (R peak value)) every cycle from an electrocardiogram acquired. The frequencies of the peak-relevant value acquired as time-series data and the magnitudes for the respective frequencies are analyzed. A peak-relevant value LF calculating device calculates an LF component (peak-relevant value LF component) from the frequency component of the peak-relevant value. An interval acquiring device acquires the interval between characteristic points of the electrocardiographic complex from the electrocardiogram acquired and the frequencies of the feature point interval acquired as time-series data to acquire the magnitudes of the respective frequency component are analyzed. An interval HF calculating device calculates the HF component from the frequency components of the feature point interval acquired and pain is judged on the basis of the variations of the peak-relevant value LF components and the interval HF components.
