Provided are an image processor and an image processing method that are capable of suppressing both density unevenness due to printing position shifts among a group of dots printed by a plurality of relative movements (or a plurality of printing element groups) and graininess. In order to accomplish this, a dot overlap rate in the printing mode in which the density unevenness stands out is made higher than the dot overlap rate in the printing mode in which other defects stand out more than the density unevenness. By doing so, it is possible to suitably adjust the dot overlap rate according to the image characteristic, and output an image having no density unevenness or graininess.