There is described an apparatus, which includes an image-forming section to form a multicolor image on a recording medium by recording the unicolor images in such a manner that the unicolor images overlap each other, based on printing image data sets of them, and a controlling section that determines at least a sub-scanning velocity in a sub-scanning direction relative to the recording medium, corresponding to a printing magnification factor, so as to adjust an output-start timing in the sub-scanning direction for every printing image data set, in response to the sub-scanning velocity determined in advance. Further, the controlling section also determines a main-scanning velocity in a main-scanning direction, corresponding to the printing magnification factor, so as to adjust output-start timings in both the main-scanning direction and the sub-scanning direction for every printing image data set, in response to the main-scanning velocity and the sub-scanning velocity, both determined in advance.