An image processing apparatus for forming a color image on an image holding member based on image data, and transferring and fixing the color image onto a print medium, comprising: a first detector, arranged to detect an image characteristic of the image transferred and fixed onto the print medium; a second detector (40, 42), arranged to detect an image characteristic of an image formed on the image holding member; a controller (28, 214), arranged to form a first pattern to detect an image characteristic on the print medium by a sequence different from a sequence for normal image formation which performs image formation based on input image data, and control an image forming condition for image formation on the image holding member based on the image characteristic of the first pattern, detected by said first detector; and a corrector, arranged to correct the image forming condition in the normal image formation, characterized in that after completion of control of the image forming condition by said controller, said corrector forms a second pattern on the image holding member using the image forming condition controlled by said controller as a first image forming condition, and holds the image characteristic of the second pattern detected by said second detector as reference characteristic, in the normal image formation, said corrector forms the second pattern in a non-image area on the image holding member using the first image forming condition, and corrects the first image forming condition based on an integral value of a difference between the image characteristic of the second pattern formed on the non-image area and detected by said second detector and the reference characteristic, in the normal image formation, said corrector repeatedly performs the formation of the second pattern on the non-image area, using the first image forming condition obtained by the previous correction, and the correction of the first image forming condition, and integrates the difference whenever the image characteristic of the second pattern on the non-image area is detected so as to perform the correction using the integral value of the difference. a first detector, arranged to detect an image characteristic of the image transferred and fixed onto the print medium; a second detector (40, 42), arranged to detect an image characteristic of an image formed on the image holding member; a controller (28, 214), arranged to form a first pattern to detect an image characteristic on the print medium by a sequence different from a sequence for normal image formation which performs image formation based on input image data, and control an image forming condition for image formation on the image holding member based on the image characteristic of the first pattern, detected by said first detector; and a corrector, arranged to correct the image forming condition in the normal image formation, characterized in that after completion of control of the image forming condition by said controller, said corrector forms a second pattern on the image holding member using the image forming condition controlled by said controller as a first image forming condition, and holds the image characteristic of the second pattern detected by said second detector as reference characteristic, in the normal image formation, said corrector forms the second pattern in a non-image area on the image holding member using the first image forming condition, and corrects the first image forming condition based on an integral value of a difference between the image characteristic of the second pattern formed on the non-image area and detected by said second detector and the reference characteristic, in the normal image formation, said corrector repeatedly performs the formation of the second pattern on the non-image area, using the first image forming condition obtained by the previous correction, and the correction of the first image forming condition, and integrates the difference whenever the image characteristic of the second pattern on the non-image area is detected so as to perform the correction using the integral value of the difference.