a blood pressure surge detection part to detect, based on predetermined determination criteria, blood pressure surges from time-series data on blood pressure of a subject that varies with pulsation;

an individual waveform acquisition part to acquire, for each blood pressure surge detected, an envelope connecting a plurality of pulse-corresponding peaks forming the blood pressure surge as an individual waveform;

a statistical processing part to perform statistical processing on a plurality of individual waveforms acquired to obtain a representative waveform and waveform variation among the blood pressure surges in the time-series data;

a display processing part to display, on a display screen, a curve indicating the representative waveform with the curve superimposed on a region indicating the waveform variation among the blood pressure surges;

creates, in a memory area, an equivalent state where the plurality of individual waveforms are relatively slid in a horizontal direction to align positions of peaks of the plurality of individual waveforms on a coordinate plane including abscissae representing a lapse of time that are identified by pulse numbers specifying the pulse-corresponding peaks and ordinates representing blood pressure variation amounts due to the blood pressure surges, and performs the statistical processing on blood pressure variation amount data on the plurality of individual waveforms for each of the pulse numbers identifying the abscissae to obtain the representative waveform and the waveform variation; and

sets, for an individual waveform that is shorter in a horizontal dimension than a longest individual waveform among the plurality of individual waveforms, a value or values of a pulse equivalent portion shorter than the longest individual waveform to zero for the statistical processing on the blood pressure variation amount data.