To identify correctly a slicing position without an influence of noise and the like, and divide the slicing position into areas indicating correctly the features of the head by specifying which of the caput, middle, lower part and base of the brain the slicing position photographed while comparing the cross sectional areas of the head and the sphenoidal sinus belong to.

An imager 1 obtains scan data obtained by scanning a subject K by the data obtainment section 2a of a processor 2, and a planigraph generation section 2b generates a planigraph from the scan data. A slicing position identification processing section 2c extracts the quantity of features of the subject K changing in accordance with the slicing positions of the planigraph from the planigraph, and identifies individual slicing positions of a series of planigraphs on the basis of the quantity of features. A slicing position association processing section 2d associates slicing positions of a series of planigraphs and those of the planigraphs of the head of a training series, and WW and WL automatic setting processing section 2e sets automatically WW values and WL values on the basis of the slicing positions of individual planigraphs.