A thermal printer comprises a thermal head and a printing data output circuit outputting printing data. A portion of the printing data is copied. The copied portion of the printing data is added to a head of the printing data to form a combination of the copied portion and the printing data. The data combination is outputted to the thermal head. The thermal head is driven with the copied portion to preheat the thermal head. Then, the thermal head is driven with the printing data to perform actual printing.
