An imaging apparatus is disclosed for diagnosis, which generates multiple horizontal cross-sectional images inside a body lumen, and a vertical cross-sectional image suitable for use by using the generated horizontal cross-sectional image. The imaging apparatus for diagnosis includes first extraction means for extracting a pixel corresponding to a cut position when a body lumen wall is cut by a plane substantially parallel to an axial direction, from a first horizontal cross-sectional image, second extraction means for extracting a pixel corresponding to a lumen surface when the body lumen wall is cut by the plane, from a second horizontal cross-sectional image, generation means for generating a vertical lumen image in such a way that a pixel obtained by projecting the pixel extracted by the second extraction means at the cut position is superimposed on the pixel extracted by the first extraction means, and display means for displaying the vertical lumen image.
