A color image forming apparatus for forming toner images by carrying out charging, exposure, and development on at least one photoreceptor drum, and forming color images by transferring the toner images onto sheets, the color image forming apparatus including: a photoreceptor drum which rotates around an axis; an exposure section which intermittently emits a light beam onto the cylindrical surface of the rotating photoreceptor drum along scanning lines parallel to the axis of the photoreceptor drum; a calculation section which calculates a printing ratio of a color image to be formed on one sheet, wherein the printing ratio is the ratio of the area covered by toner in the color image; and a timing control section which controls a timing when the exposure section emits the light beam in a direction of rotation of the photoreceptor drum based on the printing ratio calculated by the calculation section.