This invention identifies a metal area of actual measurement projection data p1 from the actual measurement projection data p1 and an actual measurement reconstruction image R1 obtained by image reconstruction of the actual measurement projection data p1, to acquire metal area identification data p1c. In the actual measurement projection data p1, 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 Y1 accurately. However, the metal area Y1 can be identified with increased accuracy. Based on the metal area identification data p1c, data replacement of the metal area Y1 of the actual measurement projection data p1 is carried out with data Z obtained from pixels adjacent the metal area Y1, thereby to acquire replacement projection data p2, which is put to image reconstruction to generate a replacement reconstruction image R2 without the metal area Y1. Since the metal area Y1 is identified with increased accuracy, the tissue adjacent the metal area Y1 of the tomographic image (replacement reconstruction image R2) can be restored with increased accuracy.
