The insertion of a peripheral intravenous catheter is often required by patients during a hospital stay. However, approximately 30% of intravenous catheters experience catheter failure. Using ultrasonography to observe the depth and diameter of a vein and to thereby perform catheter site selection is a promising procedure to prevent catheter failure. Nevertheless, it is difficult to perform this procedure, as it is associated with complicated maneuvering in which a nurse simultaneously manipulates an ultrasonographic probe, assesses veins, and inserts a catheter. In this study, a new image displaying system that consists of a camera, head-mounted display, and software is proposed. The newly developed image-processing program detects the fingertip of a user, and the system displays the reconstructed ultrasonographic image at any cross-sectional plane as indicated by the user’s finger. Additionally, veins are superimposed on the ultrasonographic image, and the depth and diameter of veins are also displayed on the image. The newly developed image-processing algorithm detects markers and fingertip in the images captured by the head-mounted camera by robustly detecting the fingertip. This aids in realizing a new ultrasonographic image displaying system. This system is used to increase the success rate of vein detection by nurses in a study of volunteers.