Embodiments for providing an elastic image are disclosed. In one embodiment, an ultrasound system comprises: an ultrasound data acquisition unit (110) configured to transmit and receive ultrasound signals to and from a living body to output ultrasound data corresponding to a plurality of frames while applying compression to the living body； and a processing unit (120) configured to extract frames from a (n-1) th frame to a (n-i) th frame on a basis of a n th frame, wherein n indicates an integer larger than one and i indicates a positive integer, detect an optimal frame for forming an elastic image among the extracted frames by using first displacement between the n th frame and each of the extracted frames based on the ultrasound data, calculate second displacement between the optimal frame and the n th frame based on the ultrasound data, and form the elastic image based on the second displacement.
