An ultrasound imaging apparatus for providing ultrasound images having different viewpoints, the ultrasound imaging apparatus comprising: an image processor configured to acquire, based on three-dimensional ultrasound data for generating a 3D ultrasound image of an object, at least one two-dimensional ultrasound image comprising at least one reference ultrasound image corresponding to at least one reference cross-section; a controller configured to set a user-designated reference cross-section obtained by moving a first reference cross-section included in the at least one reference cross-section and control generation of at least one first ultrasound image corresponding to the set user-designated reference cross-section; and a display configured to display the generated at least one first ultrasound image, wherein the user-designated reference cross-section is set to provide the at least one first ultrasound image from a different viewpoint than a viewpoint of the at least one two-dimensional ultrasound image, wherein the display is configured to display a screen comprising at least one of the at least one 2D ultrasound image and at least one of the at least one first ultrasound image, and wherein the at least one 2D ultrasound image and the at least one first ultrasound image are displayed in such a manner as to be distinguished from each other, characterised in that the image processor is configured to receive additional 3D ultrasound data related to the object, which is different from the 3D ultrasound data, wherein the controller is configured to control generation of at least one second ultrasound image corresponding to the user-designated reference cross-section based on the additional 3D ultrasound data, wherein the display is further configured to display the at least one second ultrasound image, and wherein the at least one first ultrasound image and the at least one second ultrasound image correspond to the set user-designated reference cross-section. an image processor configured to acquire, based on three-dimensional ultrasound data for generating a 3D ultrasound image of an object, at least one two-dimensional ultrasound image comprising at least one reference ultrasound image corresponding to at least one reference cross-section; a controller configured to set a user-designated reference cross-section obtained by moving a first reference cross-section included in the at least one reference cross-section and control generation of at least one first ultrasound image corresponding to the set user-designated reference cross-section; and a display configured to display the generated at least one first ultrasound image, wherein the user-designated reference cross-section is set to provide the at least one first ultrasound image from a different viewpoint than a viewpoint of the at least one two-dimensional ultrasound image, wherein the display is configured to display a screen comprising at least one of the at least one 2D ultrasound image and at least one of the at least one first ultrasound image, and wherein the at least one 2D ultrasound image and the at least one first ultrasound image are displayed in such a manner as to be distinguished from each other, characterised in that the image processor is configured to receive additional 3D ultrasound data related to the object, which is different from the 3D ultrasound data, wherein the controller is configured to control generation of at least one second ultrasound image corresponding to the user-designated reference cross-section based on the additional 3D ultrasound data, wherein the display is further configured to display the at least one second ultrasound image, and wherein the at least one first ultrasound image and the at least one second ultrasound image correspond to the set user-designated reference cross-section.