A preliminary vibration number storage unit stores a first preliminary vibration characteristic which indicates a relation between a downtime of an ejection opening and a smallest number of vibrations in preliminary vibration, the smallest number of vibrations required to enable normal preliminary ejection from the ejection opening immediately after the preliminary vibration. The downtime of each ejection opening TR is irregularly distributed within a range between zero and T1max, the range defining the first preliminary vibration characteristic, and preliminary ejection is performed subsequently to the preliminary vibration. At this point, the preliminary vibration performed is set to include N1R vibrations, the number of which corresponds to the downtime TR of the first preliminary vibration characteristic.