A plurality of pulse position candidate extraction units (38a to 38t) characterize waves included in a vibration signal from a vibration sensor (VS) using predetermined specific forms and extract respective sets of pulse position candidates. A frequency distribution calculation unit (39) calculates a frequency distribution of the pulse interval and a frequency distribution of variation in pulse intervals on each of the extracted sets of pulse position candidates. A distribution ratio calculation unit (40) calculates the distribution ratio of a modal class to the total frequency in each of the calculated frequency distributions. A selection unit (41) selects a set of pulse position candidates from among the extracted sets of pulse position candidates using the calculated relative frequencies as indicators for evaluating accuracy of the sets of pulse position candidates.
