1. An image processing system comprising: a first image processing device; and at least one second image processing device for performing an image-related process about an image in cooperation with the first image processing device via a network, wherein the first image processing device is provided with: a storing portion for storing an extension function information table including a first group of first functions and a second group of second functions, each first function being associated with one of the second functions that is needed to perform the image-related process in cooperation with the first image processing device by using the associated first function, an added function detection portion for detecting a function that is added to the first image processing device as an added function, a cooperation capable device determination portion for automatically determining, based on the extension function information table in the storing portion, which at least one second image processing device has the second function that is associated with the added function in the extension function information table and that can perform the image-related process in cooperation with the first image processing device by using the added function detected by the added function detection portion, and a function addition informing portion for sending, to a second image processing device determined by the cooperation capable device determination portion to have the second function associated with the added function, notice information that indicates that the added function is added to the first image processing device, and wherein the determined second image processing device is provided with a notice information receiving portion for receiving the notice information, and a setting portion for setting the determined second image processing device so that the image-related process can be performed by using the added function indicated in the received notice information.