A method for operating an ultrasonic diagnostic apparatus, the method comprising: transmitting, by a first probe, a first ultrasonic signal to an object and transmitting, by a second probe, a second ultrasonic signal to the object, the second ultrasonic signal being separate from the first ultrasonic signal; receiving a first echo signal which corresponds to the first ultrasonic signal and receiving a second echo signal which corresponds to the second ultrasonic signal; and displaying a first ultrasonic image which is generated based on first ultrasonic data and displaying a second ultrasonic image which is generated based on second ultrasonic data, wherein the first ultrasonic image includes an ultrasonic image of a first cross-sectional surface of the object, and the second ultrasonic image includes an ultrasonic image of a second cross-sectional surface of the object, characterised by: separating the first echo signal from the second echo signal in order to generate the first ultrasonic data which corresponds to the first echo signal and the second ultrasonic data which corresponds to the second echo signal displaying a synthesized image which is generated by synthesizing the first ultrasonic image with the second ultrasonic image, wherein the synthesized image includes a three-dimensional ultrasonic image of the object; and displaying first cross-sectional information which relates to the first ultrasonic image and second cross-sectional information which relates to the second ultrasonic image in the 3D ultrasonic image. transmitting, by a first probe, a first ultrasonic signal to an object and transmitting, by a second probe, a second ultrasonic signal to the object, the second ultrasonic signal being separate from the first ultrasonic signal; receiving a first echo signal which corresponds to the first ultrasonic signal and receiving a second echo signal which corresponds to the second ultrasonic signal; and displaying a first ultrasonic image which is generated based on first ultrasonic data and displaying a second ultrasonic image which is generated based on second ultrasonic data, wherein the first ultrasonic image includes an ultrasonic image of a first cross-sectional surface of the object, and the second ultrasonic image includes an ultrasonic image of a second cross-sectional surface of the object, characterised by: separating the first echo signal from the second echo signal in order to generate the first ultrasonic data which corresponds to the first echo signal and the second ultrasonic data which corresponds to the second echo signal displaying a synthesized image which is generated by synthesizing the first ultrasonic image with the second ultrasonic image, wherein the synthesized image includes a three-dimensional ultrasonic image of the object; and displaying first cross-sectional information which relates to the first ultrasonic image and second cross-sectional information which relates to the second ultrasonic image in the 3D ultrasonic image. separating the first echo signal from the second echo signal in order to generate the first ultrasonic data which corresponds to the first echo signal and the second ultrasonic data which corresponds to the second echo signal displaying a synthesized image which is generated by synthesizing the first ultrasonic image with the second ultrasonic image, wherein the synthesized image includes a three-dimensional ultrasonic image of the object; and displaying first cross-sectional information which relates to the first ultrasonic image and second cross-sectional information which relates to the second ultrasonic image in the 3D ultrasonic image.