An ultrasonic diagnostic device wherein: a Doppler processing unit acquires Doppler information in a living body on the basis of an ultrasonic reception signal； a velocity vector calculating unit acquires the velocity vector distribution of a blood stream in the living body on the basis of the Doppler information in the living body； and, to form a flow line showing the flow of the blood stream on the basis of the velocity vector distribution, a flow line forming unit searches for a proper start point by inversely tracing the flow of the blood stream from an initial start point along the reverse direction of the velocity vector and then forms a flow line extended from the proper start point.
