An ultrasound observation apparatus (1) including a displacement calculating section (21) that measures displacement of a subject based on an ultrasound signal, an elastic-image generating section (22) that generates an elastic image based on the measured displacement, a memory section (24) that stores generated one or more elastic images, a determination-region setting section (25) that sets a proper-image determination region for proper image determination in the elastic image according to a size of an ROI, a characteristic calculating section (26) that calculates a region characteristic of the proper-image determination region, and a proper-image determining section (27) that determines based on the region characteristic whether the elastic image is a proper image.
