When a black image region is printed, the overall pixels in the region is printed by a black ink. Then, a cation type cyan ink which makes a coloring agent in the ink insoluble is printed on the pixels of a predetermined pattern. By this, the dye of the black ink is maintained near the surface of the printing medium to increase density of the black image. At the same time, for preventing variation of tone of the black image, the pixels of the predetermined pattern are printed by a yellow ink.