Disclosed is a displacement estimating method of iteratively estimating displacement using ultrasound signals, and the method includes: transmitting, to a medium, at least one of the ultrasound signals to scan the medium receiving the ultrasound signal reflected from the scanned medium calculating a size of a window calculating a border of the window based on the calculated window size estimating displacement for each depth of the ultrasound signal, using the window with the calculated border warping the ultrasound signal based on the estimated displacement and guiding convergence of the method using the warped ultrasound signal so that a correlation value of the ultrasound signal is larger.
