To control an image forming device in an optimum state even in the case of replacing parts.

In the image forming device in which the part such as a processing cartridge constituting an image forming part is made attachable and detachable to/from a device main body and the part is used by being properly replaced with a new part, the control of image forming processing by a controlling part 31 is performed by a control parameter corresponding to the characteristic of the combination of the part. The control parameter is down- loaded from an external device through a communication means such as a network interface 44 and a modem 45 and is stored in an NVRAM 35.