1. An ultrasonic Doppler diagnostic equipment comprising; an ultrasonic probe which has piezoelectric transducers for transmitting and receiving ultrasound to and from a patient, a transmission/reception unit which transmits and receives electric signals to and from the piezoelectric transducers, a Doppler signal detection unit which detects Doppler signals at a desired range gate position, from the reception signals obtained by said transmission/reception unit, a spectrum measurement unit which measures a Doppler spectrum on the basis of the Doppler signals detected by said Doppler signal detection unit, a threshold value setting unit which sets a threshold value for power values of spectral components in the Doppler spectrum measured by said spectrum measurement unit, an average process unit which performs an average process for the spectral components of small power values selected on the basis of the threshold value set by said threshold value setting unit, from among the spectral components in the Doppler spectrum measured by said spectrum measurement unit, an image data generation unit which generates Doppler spectral image data through component processing of mean spectral components subjected to the average process by said average process unit and the spectral components of large power values not subjected to the average process, and a display unit which displays the Doppler spectral image data.