An ultrasound observation apparatus including a displacement calculating section that measures displacement of a subject based on an ultrasound signal, an elastic-image generating section that generates an elastic image based on the measured displacement, a memory section that stores generated one or more elastic images, a determination-region setting section 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 that calculates a region characteristic of the proper-image determination region, and a proper-image determining section that determines based on the region characteristic whether the elastic image is a proper image.
