PURPOSE: To enhance the pressure contact force of an ink film with a thermal head by imparting predetermined tension to said film to enhance heat transfer efficiency, by positively driving a film supply reel so as to rotate the same in the direction reverse to a film supply direction.

CONSTITUTION: Compression spring 19, 20 are inserted between gears B, D and reels 6, 7 and when force of predetermined torque or more is applied to an ink film 5, sliding is generated between the reels and the compression springs, the gear B, D, race to protect the ink film from damage. A film take-up driving part 15 is constituted so that the drive shaft of a pulse motor can be easily connected to the shaft of the drive roller 9 is film cassette when a film cassette is set to a carriage. The speed of the pulse motor is synchronous to the moving speed of the carriage during printing and control is performed so that the relative speed of the ink film to a platen always becomes zero even when the moving speed of the carriage is changed to a slow speed. At the time of non- printing, the pulse motor is stopped.