A Doppler signal detecting unit 42 and spectrum calculating unit 44 measure a Doppler spectrum from a reception signal obtained by ultrasonic wave transmission/reception with respect to a diagnosis region of an object to be examined. A local maximum/minimum detecting unit 62 detects a plurality of local maximum/minimum pairs with respect to a trace waveform generated by a trace waveform generating unit 61 on the basis of the Doppler spectrum. A feature amount selecting unit 64 selects a desired waveform from a plurality of local maximum/minimum pairs in a predetermined cardiac cycle set by a cardiac cycle setting unit 63 by using heartbeat information from a living body measuring unit 9 on the basis of a preset selection criterion. A diagnostic parameter is measured on the basis of the position information or amplitude information of the selected waveform.
