The printing apparatus includes a comparator, a threshold setting section, and an error diffusion section. The comparator compares a first threshold which is aligned with a dither mask and the image data. The threshold setting section sets a second threshold which is used in the error diffusion method to one of a low threshold and a high threshold according to results of the comparing, and sets the low threshold to a value which is smaller than a gradation range of the image data in at least a low gradation area when it is determined that the image data exceeds the first threshold. The error diffusion section generates the dot data and to calculate distribution to pixels in the vicinity of gradation errors by comparing correction data where error distribution in the image data is complete using the error diffusion method and the low threshold or the high threshold.