A copying system including an image forming device for forming an image on each of the sheets, a sheet refeeding device for successively accommodating the first copied sheets, and successively refeeding same, after the first image forming is finished, to the image forming device, to form a second image thereon, the copying system inputting the number of sheets to be copied, detecting a sheet size, determining the maximum copiable number of sheets corresponding to the detected sheet size, wherein the sheet refeeding device includes a first winding device, a second winding device and a web extended on the first and second winding device, wherein the web is wound around the first winding device while supporting the sheets thereon so as to accommodate the sheets on the first winding device, and wherein the web is unwound from the first winding device and wound around the second winding device so as to feed the sheets for the image forming process.