PURPOSE: To print a figure showing gradations for every dot in the thermal transfer method by using an ink ribbon containing an ink of a low density and applying a plurality of gradations to a thermal head at a plurality of number of times of superposing transfer.

CONSTITUTION: A printing medium 4 is set to a drum-like supporting body 3. When a printing operation is started, the drum-like supporting body 3 is rotated in a direction of an arrow A, and a thermal head 2 is moved along with an ink ribbon 1 to a direction of an arrow B. The thermal head 2 has a plurality of heat generating bodies which generate heat to transfer the ink contained in the ink ribbon 1 to the printing medium 4 thereby to form dots. One heat generating body forms one dot. When the moving speed of the thermal head 2 to the rotating frequency of the drum-like supporting body 3 and the density of the ink in the ink ribbon 1 are adjusted, it becomes possible to print each dot with a plurality of gradations.