A pulse wave signal expressing a pulse is obtained by detecting a pulse of a measurement subject using a pulse wave sensor. The pulse wave signal is stored in a storage unit. A frequency spectrum of the pulse wave signal is found by converting the time-domain pulse wave signal stored in the storage unit into the frequency domain. It is determined whether or not the measurement subject is at rest by finding a frequency range, within a predetermined total frequency range the pulse rate of a person can take on, in which an intensity of a frequency component of the frequency spectrum exceeds a first threshold, and finding whether or not a ratio of the frequency range with respect to the total frequency range is less than a second threshold. A pulse rate from the point in time when the measurement subject has been determined to be at rest is found as the measurement subject's at-rest pulse rate.