1. A printing device for forming dots on a printing medium and printing an image, the printing device comprising: a dot data generating unit for receiving image data for an image to be printed, and generating and associating with each pixel dot data indicating whether or not a dot is to be formed on the basis of a gradation value for each pixel forming the image, and a printing unit for printing the image, when dots are to be formed on the printing medium in accordance with the dot data, by dividing the formation of dots into a plurality of pixel groups having different printing conditions, and by performing at least a portion of the dot formation using the plurality of pixel groups in a common region; and the distribution of dots formed in the common region has a noise characteristic possessing a peak in the spatial frequency region on a higher-frequency side relative to a low-frequency region at or below a predetermined spatial frequency, in a case where first and second pixels belonging, respectively, to two pixel groups among the plurality of pixel groups are proximal pixels that are near to each other in the common region in a predetermined gradation range in which probabilities k1 and k2 at which a dot is formed in the first and second pixels are such that k1<0.5 and k2<0.5, a probability K of a dot being formed on both of the proximal pixels is set to be close to k1·k2.