Abstract: An apparatus adapted to adjust an interval or gap between a print head carried by a carrier unit and a printing paper disposed on a platen by sensing a paper thickness to obtain the optimum position of the print head without stepping-out a motor, including a holder, pulley, shielding plate, and a cam to rotate not only the holder and pulley with respect to the cam, but also the shielding plate with respect to the pulley independently of each other against the cam at a predetermined angle so that characters of a high quality may be printed on the printing paper.