the pulse wave on the side of peripheral blood vessels the output of this sensor 10 is applied to the pulse wave detection section 11 so that the pulse wave at the position of the subject to which the sensor 10 is attached can be detected the output of the pulse wave detection section 11 is inputted to the cpu 1 after converted into a digital signal by an a d converter 12 a key 14 is pressed either to manually measure blood pressure with the cuff 2 or to update a pulse wave propagation time fluctuation threshold u03b4t s an initial pulse wave propagation time fluctuation threshold u03b4t s and a blood pressure fluctuation threshold u03b4bp s are inputted from an input means 13 the cpu 1 executes a processing program based on signals inputted from the a d converters 7 9 12 and the key 14 to not only output necessary signals to the exhaust valve 3 the pressuring pump 4 and the like but also output processed results to a display 15 a memory rom 16 that is connected to the cpu 1 stores the processing program and a memory ram 17 that is also connected to the cpu 1 stores in process data it may.