1. An ultrasound system, comprising: a user input receiver configured to receive input information for setting at least one seed point on a two-dimensional ultrasound image from a user; an ultrasound data acquirer configured to transmit and receive ultrasound signals to and from a target object including a plurality of objects of interest and output ultrasound data; and a processor in communication with the ultrasound data acquirer, the processor being configured to form volume data based on the ultrasound data, form the two-dimensional ultrasound image and a three-dimensional ultrasound image based on volume data, set the at least one seed point on the two-dimensional ultrasound image based on the input information, detect at least one object of interest corresponding to the at least one seed point set on the two-dimensional ultrasound image from the three-dimensional ultrasound image, and perform an image process and a size measurement of the detected object of interest upon the three-dimensional ultrasound image, wherein the detection of the at least one object of interest is performed by connecting a first edge of the at least one object of interest corresponding to a first slice to a second edge of the at least one object of interest corresponding to a second slice, based on a result of comparison between a predetermined threshold value and a location difference between the first edge and the second edge, wherein the first slice and the second slice are slices that are set on the three-dimensional ultrasound image.