PURPOSE: To fix an ink sheet during transport and allow it to rotate freely during use by providing a groove on the periphery of a winding core shaft end of an ink sheet, then engaging a hook part provided on an ink sheet cassette with said groove part and providing a release device for disengagement.

CONSTITUTION: A hook 12a becomes engaged with a groove 4b provided at the winding core shaft end 4a of an ink sheet 3 by the elastic force of a hook part 12 provided on an enclosure 1. Thus the ink sheet 3 is prevented from rotating freely with an ink sheet cassette alone set in place. Next, the ink sheet cassette 11 is set at a frame 10 for a main printer system, and an inclined surface 10b provided on the frame 10 runs into the hook part 12 opposed to the surface 10b to open the hook part 12 forcibly. Consequently, the hook 12a is disengaged from the groove 4b and the ink sheet 3 becomes freely rotatable in this state.