1. An image processing apparatus used to specify an abnormal part of a subject, the image processing apparatus including one or more processors which execute a program to: calculate position adjustment data used for matching an X-ray radiographic image of a prescribed position of a specific object and a photographic image of the prescribed position of the specific object obtained by photographing the specific subject, the position adjustment data being calculated by: extracting, from the X-ray radiographic image, a contour of the prescribed position of the specific object; extracting, from the photographic image, a contour of the prescribed position of the specific object; and calculating the position adjustment data based on the extracted contour of the X-ray radiographic image and the extracted contour of the photographic image, and superpose the X-ray radiographic image and the photographic image based on the calculated position adjustment data; and display a three-dimensional X-ray CT image which has been correlated with the X-ray radiographic image and a two-dimensional biolight image which has been correlated with the photographic image in superposition, wherein the one or more processors further executes the program to: generate a sectional image of the three-dimensional X-ray CT image on a plane which is parallel with a light receiving face of the two-dimensional biolight image, and generate the sectional image of the three-dimensional X-ray CT image by applying a maximum intensity projection method to the three-dimensional X-ray CT image within a predetermined range in a direction vertical to the light receiving face of the two-dimensional biolight image.