To eliminate failure of ejection, contamination of a nozzle plate, and the like, due to adhesion of a thickened ink by providing a head cleaning liquid for removing the thickened ink adhering to the surface of the nozzle plate or a cap when water evaporates from an aqueous pigment based recording liquid.

In an ink jet printer employing an aqueous pigment based recording liquid comprising a head cleaning liquid, a suction cap 5 is provided with a head cleaning liquid supply opening 1 such that the cap 5 is filled with the head cleaning liquid supplied from a head cleaning liquid tank 3 upon opening a change-over valve 2. A thickened ink adhering to the surface of a nozzle plate or the cap 5 when water evaporates from an aqueous pigment based recording liquid is swollen efficiently with the cleaning liquid and diffused again thus preventing failure of ejection, contamination of a nozzle plate, and the like, due to adhesion of a thickened ink. The head cleaning liquid contains the dispersant, i.e., the water soluble resin component, in the aqueous pigment based recording liquid or a surfactant dissolving a fixing agent easily.