Abstract: A pattern of a character, numeral or symbol on an optical mask is selected in accordance with the designation by a character designator and irradiated with light from a printing light source. The light is converted into a light of the pattern of the designated character, numeral or symbol by a optical mask, the pattern being of a size ranging from about 20 to about 500 .mu.m, and the converted light reaches a thin layer of a dispersion imaging material formed on a recording medium to cause at least dispersion of the thin layer, thereby to print the pattern of the designated character, numeral or symbol. A recording medium support and the position of irradiation of the recording medium with the converted light are moved by a drive relative to each other, so that characters, numerals and symbols can be printed on the recording medium one by one.