PURPOSE: To detect the position of a printing head rapidly, and to increase the speed of printing treatment by setting the zone holes of a slit disk mounted to a driving section, which moves a printing section containing the printing head in parallel with a platen member, at unequal intervals.

CONSTITUTION: When the printing head 21 is moved in the right direction from a point (a), catches the first zone hole 6 (Z2) and catches the next zone hole (Z3), the position of the zone hole 6 is determined according to the distance of the zone hole 6, the number of counting of dot holes 7. Difference up to a point (b) is calculated while using the position as the starting point, the head is moved through counting by the zone hole 6 and the dot holes 7 only by the difference, and printing is started from the point (b). When the printing head 21 is positioned at a point (c) and starts printing to the left side from a point (d), the printing head 21 is moved to the right side, catches the first zone hole 6 (Z5) and catches the next zone hole 6 (Z6), and the position of the zone hole 6 is determined. A distance up to the point (d) toward the left side from the point is counted by the zone hole 6 and the dot holes 7 and the head is moved, and the head starts printing from the point (d).