Atherosclerosis plays the major role in myocardial infarction and stroke and its pathophysiology is closely related to blood flow. Among clinical imaging modalities, ultrasound has the highest temporal resolution. Doppler ultrasound has been clinically applied for blood flow measurement and several parameters obtained with Doppler have been considered as essential for diagnosis. However, conventional Doppler method merely measures one-dimensional component of the blood flow along the ultrasonic beam. Based on previous approaches with multi-angle Doppler measurement for two-dimensional (2D) blood flow, this study aims to expand 2D flow measurement into three-dimensional (3D) flow estimation by applying continuity equation on multiplane 2D velocity mapping. The algorithm was validated by numerical simulation based on computational fluid dynamics and comparison with particle image velocimetry of carotid artery model. The method visualized 3D spiral flow in the carotid artery bifurcation model where 2D blood flow showed Iaminar flow. Clinical application of 3D blood flow visualization will provide important information on pathophysiology in common sites of atherosclerosis.