An image-forming apparatus includes image-forming sections, a density detector, and a controller. Each image-forming section has an exposing unit and a developing unit. The image-forming section prints an image of a density detection pattern having a plurality of pattern segments of different duties. The image is printed on a print medium under a predetermined printing condition. The density detector outputs detection values indicative of densities of the plurality of pattern segments printed on the print medium. The controller determines a correction value based on the detection values and corresponding target values of density to modify the printing condition for the image-forming sections. The correction value may be a correction to the amount of light to be emitted from the exposing unit. The correction value may be a correction to the developing voltage to be supplied to the developing unit. The correction value may be weighted.