A method of displaying an elastic image, comprising: a) performing transmission/reception of an ultrasound signal along a plurality of scan lines set on a target object to obtain first ultrasound data, the target object including a plurality of tissues; b) performing transmission/reception of an ultrasound signal along a plurality of scan lines set on the target object by applying a stress to the target object to obtain second ultrasound data; c) calculating displacements of the tissues based on the first and second ultrasound data; d) calculating strains in the tissues based on the calculated displacements; e) forming an elastic image based on the calculated strains and a graph indicating changes of the tissues for the respective scan lines; and f) displaying the elastic image together with the graph.