In an image-forming system, when the user inputs an instruction for image processing to an input section in a digital copying machine, the control section of the digital copying machine outputs image information of a document to a host computer. The host computer carries out a predetermined image process on the inputted image information, and outputs the processed image information to the digital copying machine through a transferring device. The control section of the digital copying machine supplies the processed image information to an image-recording section, and the image-recording section forms a visual image based on the image information. With this arrangement, merely by installing necessary processing functions in the host computer, it becomes possible to eliminate the need for purchasing a new digital copying machine to replace the older one with relatively outdated functions, and also to reduce the burden on users on an economic basis.