Embodiments for providing a motion image are disclosed. In one embodiment, by way of non-limiting example, an ultrasound system comprises: an ultrasound data acquisition unit configured to form transmit signals having different phases between a nth frame and a (n+1)th frame, transmit and receive ultrasound signals to and from a target object based on the transmit signals to output ultrasound data; and a processing unit in communication with the ultrasound data acquisition unit, the processing unit being configured to form motion data corresponding to motion of the target object based on a phase difference between the ultrasound data corresponding to the nth frame and the ultrasound data corresponding to the (n+1)th frame, and form a motion image corresponding to the motion of the target object based on the motion data.