A quantization method includes: quantizing first image data, and converting the first image data to second image data that indicates a binary or multivalued quantized pattern with a smaller number of gradations than that of the first image data, for which dots are arranged by the same recording element for individual pixels of a pixel column along a first direction respectively and dots are arranged at a plurality of different timings for individual pixels of a pixel column along a second direction orthogonal to the first direction; and optimizing the quantization in at least some gradations, and reducing dispersion of a generation frequency of a dot arrangement for each relative positional relation between a pixel of interest in the case that individual pixels within the quantized pattern are successively defined as the pixel of interest and a plurality of vicinity pixels positioned in the vicinity of the pixel of interest.