An ultrasound diagnostic apparatus for providing on a display an ultrasound image including a target object and a pointer movable on the ultrasound image, comprises: an ultrasound image providing unit configured to provide an ultrasound image including a target object; a contour line extracting unit configured to extract a contour line of the target object in the ultrasound image; a coordinate recognizing unit configured to detect cross points while the pointer crosses the contour line and recognize the coordinates of the corner points; a user input unit configured to receive instructions from a user, said instructions including a selection instruction to select measure points among the cross points and a measure instruction to measure a size of the target object; a measuring unit configured to measure a size of the target object in response to the measure instruction based on coordinates of the measure points selected in response to the selection instruction; and an output unit configured to output the ultrasound image, the pointer, the contour line, the measure points and the size of the target object.