this invention concerns an image processing device for adjusting the density of an image and an image reading device incorporating the image processing device and aims to enhance the repeatability of pseudo - gradient without reference to density distribution of the image . the image processing device which fulfills the purpose of compensating the gradient of image data consisting of multivalue digital signals comprises means me1 to me3 for storing a plurality of gradient compensation data t1 to t3 having mutually different contents of compensation , means for detecting a contrast of an image on the basis of a group of image data conforming to one image , and means for switching the contents of compensation for the image data by selecting one of the three gradient compensation data t1 to t3 in conformity with the contrast .