Ultrasound image processing method and ultrasound diagnostic device using the method, the method including: acquiring frame signals generated at different time points; generating, by using the frame signals, a first motion map composed of pixel areas each having a motion, the motion indicating an inter-frame signal change and calculated from corresponding pixel areas of the frame signals; holding a second motion map and creating a third motion map by performing a calculation using motions in the first and second motion maps; and adding emphasis to a frame signal by using the third motion map and generating an ultrasound image from the frame signal. In the method, after the calculation using motions, the third motion map is held in place of the second motion map.