In a head unit of a printer, a head (5A) has outlet rows (611, 612, 621 and 622) arranged along a first tilt direction and a gap between outlets in the outlet rows (611 and 612) is interpolated with a outlet in the outlet rows (621 and 622) by a slight tilt. A head (5C) adjacent to the head (5A) is tilted in a second tilt direction opposite to the first tilt direction. In the printer, a plurality of dots are formed, being aligned on a piece of printing paper in the first tilt direction by performing an ejection control simultaneously for all outlets in each outlet row of the head (5A) and subsequently a plurality of dots are formed, being aligned on the piece of printing paper in the second tilt direction by performing an ejection control simultaneously for all the outlets in each outlet row of the head (5C), to make both rows of dots continuous. Through this operation, the printer can easily perform high-resolution printing without such a complicate ejection control as to control ejection of ink for each outlet (7).
