1. A multi-planar reformatted image generating apparatus comprising: a three-dimensional image data storing unit for obtaining three-dimensional image data of a subject obtained by reformatting, on the basis of image data of a plurality of cross-sectional images in a three-dimensional region of the subject, the plurality of cross-sectional image data, and storing the obtained three-dimensional image data; a multi-planar reformatted image generating unit for generating at least one multi-planar reformatted image which is a two-dimensional image of the subject on the basis of image data of a three-dimensional region in the subject stored in the three-dimensional image data storing unit; a luminal organ information extracting unit for extracting information concerning the shape of the three-dimensional region of a predetermined luminal organ, on the basis of the image data of the three-dimensional region in the subject stored in the three-dimensional image data storing unit; an extracted luminal organ image superimposing unit for superimposing an extracted luminal organ image, in which a result of the luminal organ extraction obtained by the luminal organ information extracting unit is reflected, on a predetermined cross-sectional image in the at least one multi-planar reformatted image to correspond to the predetermined cross-sectional image in the multi-planar reformatted image; and a route setting unit for setting a route for inserting an endoscope in a duct of the luminal organ, on a superimposed two-dimensional image wherein the extracted luminal organ image is superimposed on the multi-planar reformatted image.