PURPOSE: To remove bubbles and solids in an ink path leading to a recording head from an ink tank by utilizing an liquefied gas as a means to raise the pressure of gas in a cleaning method in which ink is sent under pressures from an ink-housing bag to the recording head during non-recording period and the ink is discharged from the recording head.

CONSTITUTION: When purge is needed during non-recording period, the solenoid of a connector 14 is turned ON by an automatic or manual switch, and a movable shft 15 is pushed down and closely contacted with a cartridge box 6 through a pressing part 17. When a control valve 19 is opened under the condition, liquefied gas in a liquefied gas bomb 16 is discharged in the form of gas stream from the control valve 19 and jetted into the cartridge box 6, an ink-housing bag 5 incorporated is compressed, and ink present is compressed. The ink is sent under pressures from an ink supply pipe 10 and a filter 11 into the recording head and then discharged from a nozzle 1 to the outside. At that time, air bubbles and foreign matter in the nozzle 1 and the recording head are discharged altogether.