An ink which is supplied from an ink cartridge via an ink supply tube is stored in an ink tank, and is supplied to a recording head. The ink cartridge is detachably connected to the ink supply tube. At every predetermined time interval, a maintenance unit carries out an air discharge operation to discharge air accumulated in the ink tank, through an air discharge passage. Moreover, even at a time shorter than the predetermined time interval, when a frequency of replacement of the ink cartridge is higher than a predetermined value, the air discharge operation is carried out and the air accumulated in the ink tank is discharged.