A thermal transfer printer includes: an ink ribbon conveyor unit that conveys an ink ribbon; a sheet conveyor unit that conveys a sheet; a dummy pattern generation unit that generates a dummy pattern; an image data generation unit that generates print image data joining n screens together, the print image data including the dummy pattern inserted between two adjacent screens among the n screens; a thermal head that transfers a dye coated on the ink ribbon in accordance with the print image data; and a peeler unit that peels the ink ribbon from the sheet. An average density of the dummy pattern is equal to an average density of the image over an area equivalent to a distance between a tail end portion of the thermal head and the peeler unit, on one screen that follows the dummy pattern.