A thermal transfer printing apparatus includes a storage to store a plurality of density adjustment parameters that are each associated with a corresponding one of a plurality of first-page calibration patterns and a plurality of second-page calibration patterns, a density adjustment processing part to adjust data on a color gradation value of a first-page superimposing portion and data on a gradation value of a second-page superimposing portion using their respective associated density adjustment parameters, and a printing part to make a print on recording paper to form a plurality of printed calibration patterns that include a printed superimposing portion where the first-page superimposing portion and the second-page superimposing portion are superimposed on each other based on data on color densities adjusted by the density adjustment processing part. A color density of the printed superimposing portion printed on the recording paper varies for each of the printed calibration patterns.