The present invention relates to a device and a method for processing and transmitting image data in a wireless AV system. The present specification provides a device comprising: an external device interface unit configured to receive an external input signal including an actual image (an actual picture); a control unit connected to the external device interface unit and configured to detect the external input signal and produce information on the external input signal; an image processing unit connected to the control unit, receiving, from the control unit, at least one among the external input signal and the information on the external input signal, determining an image compressibility on the basis of the information on the external input signal, and outputting a compressed image based on the determined image compressibility; and a communication unit for transmitting the compressed image through a wireless channel.