A blood pressure measurement device accurately calculates an index useful in determining the degree of arteriosclerosis by accurately detecting a difference in time of appearance of a ejection wave and reflected wave in a blood pressure waveform. The device sets a threshold value based on an index that expresses a characteristic of the blood pressure waveform with respect to the point of appearance of the reflected wave in the blood pressure and estimates a rise point of the reflected wave by calculating an x-coordinate value of a point based on a maximum amplitude of the reflected wave and the threshold value. The device obtains the index of degree of arteriosclerosis by calculating a time difference in appearance between the ejection wave and the reflected wave based on the estimated rise point of the reflected wave.