To provide a network image forming system capable of retaining the secrecy of an image data.

In the network image forming system having an image forming apparatus 10 and an external storage device 21 connected through a network 30, the image forming apparatus 10 includes a system control portion 1 for preserving an image read in from a scanner portion 3 or a received image data, and for printing by a plotter portion 4 by calling the image data preserved in the external storage device 21.