1. A method of operating an ultrasonic diagnostic apparatus, the method comprising: displaying an ultrasonic image in a first region of a display unit; selecting a region of interest (ROI) in the ultrasonic image; displaying a scan conversion image and a certain magnification in a second region, wherein the scan conversion image is generated by enlarging or reducing an image corresponding to the selected ROI at the certain magnification; and acquiring a measurement value of the ROI on a basis of the scan conversion image, wherein resolution of the scan conversion image is equal to or higher than resolution of the ultrasonic image.