Transoral carotid ultrasonography (TOCU) is a powerful tool for evaluating internal carotid artery lesions located from the carotid bifurcation to the second cervical vertebra. In recent case reports, contrast-enhanced transoral carotid ultrasonography (CETOCU) and superb micro-vascular imaging (SMI) which are useful in endovascular therapy are emerging. Lately, three-dimensional (3D) and four-dimensional (4D) ultrasound have been widely used in angiology. We developed 3D-TOCU and used it in a healthy man to confirm the utility of the 3D technique. Mutual conversion to the long axis from the short axis is possible based on an image of a vessel using multiplanar reconstruction (MPR) in 3D-TOCU. By operating the ultrasound machine, a novice examiner can obtain an adequate image in TOCU. TOCU performed with single sweep mode can produce the intraluminal vessel image from proximal to distal on the short axis, which is not possible with conventional TOCU. 3D-TOCU is expected to be clinically useful.