1. An ultrasonic imaging apparatus comprising: a 3D tomographic image data capturing device configured to capture 3D tomographic image data from a 3D region inside a subject; a region-of-interest setting device configured to set a 3D region of interest corresponding to the 3D region in an image memory that stores the 3D tomographic image data; a surface image extracting device configure to extract data on a surface image of a massive tissue included in the 3D region using the 3D tomographic image data, wherein the surface image is within the 3D region of interest; a stereoscopic display generating device configured to generate stereoscopic display data to display the surface image data stereoscopically; and a display device configured to display the stereoscopic display data, wherein said region-of-interest setting device is further configured to: display a 2D tomographic image of a 2D region including the massive tissue on said display device; receive a manual setting of a marker indicating a periphery of the massive tissue in the 2D tomographic image; and generate the 3D region of interest with the marker in the vicinity of the center according to data on the marker's position in the 2D tomographic image.