A scanning device includes a first tray, a second tray, a detection module, a scanning module, and an image processing module. The first tray has an identification element. When the scanning device scans the first tray, the detection module detects the identification element so as to generate a first signal. When the scanning device scans the second tray, the detection module does not detect the identification element so as to generate a second signal. The image processing module uses a first group of parameters to process the scanned image when receiving the first signal. The image processing module uses a second group of parameters to process the scanned image when receiving the second signal.