Provided is a method of adjusting brightness of an ultrasound image including: generating at least one first image representing a region of interest (ROI) by using echo signals corresponding to ultrasound waves irradiated toward the ROI； adjusting brightness of the at least one first image based on an external signal for selecting at least one selected from a plurality of prestored gradation data and a plurality of prestored image data； and generating a second image representing the ROI based on the adjusted brightness.
