A control device mounted in an image forming apparatus includes a region searching for unit searching for a region adapted to measure colors in an image; a color measurement unit configured to measure colors of the superimposed color toner image in the region; a storage unit storing measured colors and densities proportional to area ratios of primary color toner images in the superimposed color toner image in the region; and a correction amount determination unit determine correction amounts corresponding to the setting values expressing the tone reproduction curves to minimize the difference between the measured colors and the reference colors.