An ultrasound image generation apparatus (10) includes: a first motion estimation unit (10A) which estimates, as a first motion vector, a motion vector of the ultrasound probe using a first estimation method, the motion vector indicating the movement between images of the respective ultrasound signals a second motion estimation unit (10B) which estimates, as a second motion vector, a motion vector of the ultrasound probe using a second estimation method different from the first estimation method in direction dependency of estimation accuracy and a position reconstruction unit (10C) which (i) assigns, based on a direction of the first motion vector or a direction of the second motion vector, weights to the first and the second motion vectors, (ii) combines the weighted first and second motion vectors into a combined motion vector, and (iii) constructs an ultrasound diagnostic image of a subject using the combined motion vector and the images.
