A medical image diagnosis device according to the present invention has a medical image acquiring unit that acquires a medical image, a three-dimensional image constructing unit that constructs a three-dimensional image containing a motional internal organ region in the medical image, a sectional image generator that generates a two-dimensional sectional image serving as a reference image from the three-dimensional image, a region dividing unit that divides the reference image into plural regions on the basis of a criterion for region division, and a region-of-interest setting unit that calculates motion states of the plural regions, specifies at least one region of the plural regions on the basis of the calculated motion states, and sets as a region of interest a region of the medical image in which the specified region is contained.
