A liquid ejection head is caused to eject liquid droplets at a region where no target medium is placed, such that such that a first prescribed number of liquid droplets are flushed from each of the nozzle orifices in the nozzle arrays of the first group, and a second prescribed number of liquid droplets are flushed from each of the nozzle orifices in the nozzle arrays of the second group. At least a part of the first prescribed number of liquid droplets and at least a part of the second prescribed number of liquid droplets are flushed by alternately performing a first unit operation for flushing a third prescribed number of liquid droplets which is smaller than the first prescribed number and a second unit operation for flushing a fourth prescribed number of liquid droplets which is smaller than the second prescribed number.