there is provided an ultrasonic doppler blood - flow meter which can suppress the occurrence of unwanted frequency components by suppressing the jump of signal to thereby produce images of high quality a dc feedback circuit is provided which negatively feeds back a doppler deviated signal produced from an integrator to the input thereof . the feedback amount of the dc feedback circuit is changed in synchronism with the timing for switching between the b - mode transmission / reception sequence and the doppler mode sequence to prevent a jump of a signal at the commencement of the doppler mode . the feedback amount of the dc feedback circuit is made to be different for the gate moving sequence and the doppler mode sequence , thereby preventing a jump of a transient signal due to a discontinuous input signal at the commencement of the doppler mode .