The object of the invention is to provide an image processing apparatus that greatly enhances color conversion precision by considering in-plane uniformity and nonlinearity such as a gradation characteristic and a multiple transfer characteristic in an image formation device when color variation in a plane of the image formation device is considered in color conversion. An arithmetic section converts a signal L* to an image recording signal K of the image formation device based upon a lightness L* signal input from an image input device, a recorded position coordinate signal x in a horizontal scanning direction on paper and the rotation angle signal y of a photo conductor showing a recorded position coordinate in a vertical scanning direction on the photo conductor from the image formation device in consideration of color variation caused due to an image formation process on the photo conductor in the image formation device and the signal L*. This color conversion can be made using n-dimensional DLUT for example. The image recording signal K is output to the image formation device and an image is formed.