PROBLEM TO BE SOLVED: To automatically adjust at least obtained two images so that the images can be viewed in the same way, irrespective of the difference in the kind of a modality and in an imaging method.SOLUTION: A window processing condition deciding means (50) of an image processing device (14) refers to a gradation pattern table (46) storing gradation patterns of a predetermined part according to a modality and an imaging method, thereby searching a gradation pattern according to the predetermined part of at least the two input images which are different in modality and/or an imaging method. The means (50) decides window processing conditions for the two input images according to the searched gradation pattern. A window processing means (52) performs window processing for the two input images on the basis of the window processing conditions.
