An image forming device, has an image carrier on which a latent image is formed, and a development device to which a plurality of development units for containing developer with the same color are detachably installed, and development is performed by attaching the developer of the development unit on the latent image of the image carrier. And the image forming device further has calibration control unit for forming the latent image of a predetermined patch pattern on the image carrier, developing the image by the developer of the development unit, detecting the developed patch pattern and deciding control parameters, and the calibration control unit performs calibration by only apart of the development units or by one development unit out of the plurality of development units.