A wireless device for providing a screen sharing service with an external apparatus according to an embodiment of the present invention comprises: a wireless communication unit for receiving an image signal corresponding to a source image that the external apparatus is displaying: a display unit for displaying a mirroring image on the basis of the image signal; and a processor for controlling the display unit and the wireless communication unit. The processor can receive, from the external apparatus, a first message inquiring about support for an image quality setting function for the image being displayed by the external apparatus, and transmit a second message to the external apparatus in response to the first message, wherein the second message includes a response to the inquiry about whether the image setting function is supported.