A display device comprising: a display unit formed to be flexible and configured such that at least one portion of the display unit is modifiable by being protruded or recessed; and a controller configured to display an output target image on the display unit and control to modify the display unit based on a visual attribute of a portion of the output target image, wherein the controller is configured to determine a modification target area in the output target image based on the visual attribute of components included in the output target image, and modify a display area of the display unit corresponding to the determined modification target area, wherein the components include at least one of points, lines, or surfaces forming the output target image, wherein the visual attribute is at least one of an aggregation degree of the points forming the output target image, curved degrees of the lines forming the output target image, or brightness degrees of the surfaces forming the output target image, wherein the controller is configured to divide the output target image into a plurality of reference images having a predetermined size, and determine, as the modification target area, an area corresponding to at least one reference image selected based on a visual attribute of components in each of the plurality of reference images, wherein the controller is configured to select the at least one reference image from the plurality of reference images which has a value corresponding to at least one visual attribute of the components in the at least one reference image that is equal to or greater than a predetermined reference value of the at least one visual attribute, wherein the controller controls the display unit such that a degree of protrusion or recession of the display area is changed according to a difference between a value of the at least one visual attribute and the predetermined reference value of the at least one visual attribute. a display unit formed to be flexible and configured such that at least one portion of the display unit is modifiable by being protruded or recessed; and a controller configured to display an output target image on the display unit and control to modify the display unit based on a visual attribute of a portion of the output target image, wherein the controller is configured to determine a modification target area in the output target image based on the visual attribute of components included in the output target image, and modify a display area of the display unit corresponding to the determined modification target area, wherein the components include at least one of points, lines, or surfaces forming the output target image, wherein the visual attribute is at least one of an aggregation degree of the points forming the output target image, curved degrees of the lines forming the output target image, or brightness degrees of the surfaces forming the output target image, wherein the controller is configured to divide the output target image into a plurality of reference images having a predetermined size, and determine, as the modification target area, an area corresponding to at least one reference image selected based on a visual attribute of components in each of the plurality of reference images, wherein the controller is configured to select the at least one reference image from the plurality of reference images which has a value corresponding to at least one visual attribute of the components in the at least one reference image that is equal to or greater than a predetermined reference value of the at least one visual attribute, wherein the controller controls the display unit such that a degree of protrusion or recession of the display area is changed according to a difference between a value of the at least one visual attribute and the predetermined reference value of the at least one visual attribute.