In an ink-jet printing apparatus, upon turning on the power source of the printing apparatus, a stirring operation of ink in the main tank is performed for a given period of time, and during subsequent printing operation, the stirring operation in the main tank is performed for the given period at every predetermined elapsed time period. By this, the printing operation for a long period can be performed employing ink having a water insoluble dye without causing a problem of admixing of bubble or so forth caused by stirring of the ink in the main tank.