US Patent 7104960 Noninvasive sphygmomanometer

A noninvasive sphygmomanometer capable of obtaining an accurate blood pressure value is provided without complicating a structure and with little time-consuming work. A photointerrupter 31, a wave-shaping circuit 75, a rotation number counting circuit 77, and a discharge amount calculating circuit 78 which measure a discharge amount of a pressure pump 13, and an arm circumference length detecting circuit 79 which calculates an arm circumference length of a subject person based on a relationship between a pressure in a bladder 8 provided in an armband 9 and the measured discharge amount of the pressure pump 13 is provided. Then, a blood pressure value is corrected based on the calculated arm circumference length.