A method includes pressurizing a cuff of a blood pressure measurement device that is wrapped around a measurement site of a patient, measuring the patient's blood pressure and pulse period during and before depressurization of the cuff, calculating a threshold value range of the pulse period based on data of a past measured pulse period of the patient, determining whether the measured pulse period is within the threshold value range of the past measured pulse period, if the measured pulse period is determined to be within the threshold value range of the past measured pulse period both during and before depressurization, displaying that the patient was in the rest condition, and if the measured pulse period is determined not to be within the threshold value range of the past measured pulse period either during or before depressurization, displaying that the patient was in the unrest condition.