Cardiac blood flow patterns such as the vortex flow pattern inside the left ventricle have been studied to provide new information for the diagnosis of the pumping function of the human heart. Complex blood flow is visualized by imaging echo speckles of blood particles because the speckle-like texture translates to the motion of blood particles. We proposed an imaging method for echo speckles of blood particles using high-frame-rate ultrasound for the visualization of the intracardiac blood flow direction. High-frame-rate ultrasound is useful for continuously observing the fast motion of echoes from blood particles in the heart. In the present study, weighting by coherence and compounding the magnitudes of echo signals in different transmissions were introduced to visualize weak echoes from blood particles. The feasibility of the visualization of cardiac blood flow using high-frame-rate ultrasound was demonstrated by basic and in vivo experiments.