PURPOSE: To save the time and labor required for fine adjustment and at the same time, obtain the setting value of a highly stable gap.

CONSTITUTION: A printing head is of such a structure that a distance between the head and a platen can be changed using a stepping motor 14, and is activated by a command from a motor rotation command part 20. In addition, a slit disc 7 and a slit sensor 8 determine whether the printing head comes in contact with the surface of a printing sheet. If the tip of the printing head comes in contact with the surface of the printing sheet 10 following the movement of the printing head 1 in a pressing direction using the stepping motor 14 and then the out-of-step state of the stepping motor 14 is detected, during a gap adjustment action, the stepping motor 14 is reversed by a constant number of steps SG+SO to fetch back the printing head. After that, the stepping motor 14 is rotated by SO step again in the pressing direction.