A dither matrix generator includes: a main-cluster generator that generates at least one main-cluster in a matrix, the matrix including a plurality of cells, the main cluster area including a predetermined number of cells; a sparest searcher that searches a sparest area in the matrix, the sparest area being the area other than the area of main-cluster; a sub-cluster generator that generates at least one sub-cluster area, the sub-cluster area including a smaller number of cells than that of the main-cluster; a dither value allocator that allocates dither values to the plurality of cells of the matrix, the cells in the main-clusters having smaller dither values than those in the sub-cluster areas, the cells in the sub-cluster areas having smaller dither values than those in the areas other than the main-cluster and the sub-cluster areas.