A master device comprising: a display unit; a memory comprising a frame buffer configured to store pixel data; a control unit configured to control the display unit to display a screen; and a communication unit configured to: communicate with a client device; and transmit, to the client device as part of a mirroring service, data corresponding to the entire displayed screen; wherein the control unit is further configured to: receive, from the client device after completion of the mirroring service, mirroring screen information comprising information indicating a position of a first region of the entire displayed screen; generate high image-quality data of the first region using stored pixel data corresponding to the first region, based on the information indicating the position of the first region; and determine a second region of the entire displayed screen based on the information indicating the position of the first region, and generate low image-quality data of the second region using stored pixel data corresponding to the second region, wherein the second region corresponds to the entire displayed screen excluding the first region; and wherein the communication unit is further configured to transmit the high image-quality data and the low image-quality data to the client device; and wherein the stored pixel data includes the stored pixel data corresponding to the first region and the stored pixel data corresponding to the second region. a display unit; a memory comprising a frame buffer configured to store pixel data; a control unit configured to control the display unit to display a screen; and a communication unit configured to: communicate with a client device; and transmit, to the client device as part of a mirroring service, data corresponding to the entire displayed screen; communicate with a client device; and transmit, to the client device as part of a mirroring service, data corresponding to the entire displayed screen; wherein the control unit is further configured to: receive, from the client device after completion of the mirroring service, mirroring screen information comprising information indicating a position of a first region of the entire displayed screen; generate high image-quality data of the first region using stored pixel data corresponding to the first region, based on the information indicating the position of the first region; and determine a second region of the entire displayed screen based on the information indicating the position of the first region, and generate low image-quality data of the second region using stored pixel data corresponding to the second region, wherein the second region corresponds to the entire displayed screen excluding the first region; and receive, from the client device after completion of the mirroring service, mirroring screen information comprising information indicating a position of a first region of the entire displayed screen; generate high image-quality data of the first region using stored pixel data corresponding to the first region, based on the information indicating the position of the first region; and determine a second region of the entire displayed screen based on the information indicating the position of the first region, and generate low image-quality data of the second region using stored pixel data corresponding to the second region, wherein the second region corresponds to the entire displayed screen excluding the first region; and wherein the communication unit is further configured to transmit the high image-quality data and the low image-quality data to the client device; and wherein the stored pixel data includes the stored pixel data corresponding to the first region and the stored pixel data corresponding to the second region.