1. A medical image diagnosis device comprising: an image generator configured to obtain image data of a tissue of an object and generate an image of the tissue of the object based on the image data; a calculator configured to calculate motion vectors of a plurality of measurement points of the generated image to obtain a first motion characteristic amount; an input instrument configured to specify an observation region of the image; a database in which a characteristic amount of the motion vectors of the plurality of measurement points in respective images of a plurality of different observation regions is set and stored in advance; a checker configured to read a second motion characteristic amount of the observation region specified by the input instrument from the database and detect a position where the first motion characteristic amount coincides with the second motion characteristics amount; and an ROI (region of interest) setting unit configured to set a region of interest in the generated image based on the position where the first motion characteristic amount coincides with the second motion characteristic amount.