To provide an image-forming system which efficiently transmits image data, without affecting other devices between an image-forming device and an information processor or between a plurality of image-forming devices without increasing the load on equipment.

This system transmits information between an image-forming device 1 and an information processor 3 via a network. In this case, the processor 3 has at least either an expansion function expanding compressed data or a compressing function compressing data into compressed data, and the compressed data are transmitted between the device 1 and the processor 3.