To solve a problem that the density of ink is lowered as the residual quantity of ink decreases and the print density is lowered gradually.

In color conversion processing being executed by a color conversion module 10c1 in print data generation processing executed by a printer driver 10c, used quantity of ink is determined for ink filling ink cartridges 32 and 33 and variation of ink is determined therefrom. Based on the variation of ink, a correction factor of print density is determined by retrieving a correction factor table TBL and a color conversion table LUT is corrected based on the correction factor thus correcting print density. Variation of print density due to variation of ink caused by aging is thereby prevented and printing can be carried out with a constant print density.