A system to set a scan image as wallpaper includes a scanner and a host. The scanner includes a scanning part to scan a document and to form image data, an interface to communicate with another medium, and a control part to control the scanning part and the interface to transfer the image data to another medium via the interface. The host is connected with the scanner, and includes a driver program unit to drive the scanner, an application program unit to generate an image file by processing the image data transferred from the scanner, and a monitor to display the image file. When an automatic wallpaper setting is selected, the host processes the image data formed by the scanner according to a scan command to generate an image file, and automatically sets the image file as wallpaper on the monitor. Accordingly, user inconvenience in the process of scanning and setting wallpaper can be prevented, and wallpaper of image quality and size corresponding to a screen size and resolution of the monitor can be provided.