A method for generating a region of interest (ROI) wherein in setting ROIs in biological tissues to be compared, burden on a subject can be reduced and the reproducibility of elasticity measurement improved, including: setting candidate points in an arbitrary designated region in a notable tissue in a contrast image of an object designated by an input device determining partial differential values of pixel values in a two-dimensional direction in the contrast image and thus detecting a tissue boundary acquiring a shortest distance between the detected tissue boundary and each point, and setting a circle or polygonal region inscribed in the circle having the maximum shortest distance as a radius around the candidate point having the maximum shortest distance as a region of interest and imaging the region of interest and superimposing it on the contrast image and displaying it on an image display unit.
