PURPOSE: To prevent deformation of a tube and a damage on the thermal head caused by printing while pressing a thermal head against the tube in a tube printer for printing letters or the like on the flexible tube such as a thin plastic tube.

CONSTITUTION: A shaft 5 is adapted to fit a tube 1 therein. A tube moving means 4 is provided for moving the shaft 5 to a position facing a thermal head 13 of a print unit 12; and a roller 15 as a driving means, for rotating the tube 1 fitted to the shaft 5. The tube is rotated by driving of the roller with the shaft 5 facing the thermal head 13, thus carrying out printing. Consequently, it is possible to carry out printing without deforming the tube and to keep constant the printing pressure of the thermal head to the tube.