The present invention relates to an image output device having an image quality adjustment function. A method for controlling a mobile terminal so as to control the image quality of a plurality of image output devices according to an embodiment of the present invention comprises the steps of: generating a preview image on the basis of images corresponding to the plurality of image output devices, received through a camera, and extracting image quality information of the plurality of image output devices using the images corresponding to the plurality of image output devices, included in the preview image; and transmitting the extracted image quality information or image quality correction data corresponding to the image quality information to at least one image output device, the image quality of which is to be adjusted, among the plurality of image output devices.