This invention identifies a metal area of actual measurement projection data from the actual measurement projection data and an actual measurement reconstruction image obtained by image reconstruction of the actual measurement projection data, to acquire metal area identification data. In the actual measurement projection data, a resulting image has pixel values in the metal area such as of wire or screws, for example, not so different from pixel values of other areas, which makes it difficult to identify the metal area accurately. However, the metal area can be identified with increased accuracy. Based on the metal area identification data, data replacement of the metal area of the actual measurement projection data p1 is carried out with data obtained from pixels adjacent the metal area, thereby to acquire replacement projection data, which is put to image reconstruction to generate a replacement reconstruction image without the metal area. Since the metal area is identified with increased accuracy, the tissue adjacent the metal area of the tomographic image (replacement reconstruction image) can be restored with increased accuracy.
