A clustered-dot screen design method, a device to perform the clustered-dot screen design method based on human vision characteristics and printer model characteristics, and an image-forming apparatus to output binary images using designed screens. The clustered-dot screen design method based on the human vision characteristics and the printer model characteristics includes determining positions of a plurality of clustered-dot centers using a predetermined method, and designing a screen by growing specific sub-dots about the cluster centers using a predetermined algorithm according to position information of the cluster centers, the human vision characteristics, and the printer model characteristics. The clustered-dot design method has a high tolerance for defects of printers, since a dot growth sequence about the cluster centers is designed in an optimized method based on the human vision characteristics and the printer model characteristics to have an optimized image quality in output images of the printers, and the dots are clustered about the cluster centers.