The present invention provides a dot data processing apparatus for generating data of dots to be formed on a printing medium. The apparatus includes: a decoding preparation unit that prepares a decoding table for pixel groups, each of the pixel groups grouping together a plurality of pixels that constitute a unit of dot formation, the table containing output dot arrangements and code values in a number of identifiers assigned to the pixel groups, the output dot arrangements and code values being associated, the output dot arrangements representing the dot on-off states for the pixels in the pixel groups, the code values assuming a prescribed range of values; a code value receiving unit that receives code values derived as a result of encoding of image data representing an image with a prescribed tone number, the encoding being performed for the each pixel group as an encoding unit; a decoding unit that acquires the output dot arrangement based on the received code value and the identifier assigned to the pixel group, by means of lookup in the decoding table; and a dot data output unit that outputs dot data which represents an arrangement of dots to be formed on a printing medium, in accordance with the acquired output dot arrangement.