Ink ejection problems of black ink nozzles are compensated for by forming dots by mixing cyan, magenta and yellow inks without reducing print quality. When a nozzle that discharges black ink becomes unable to properly eject ink, cyan, magenta, and yellow inks are ejected from respective nozzles to the discharge area on the recording medium to which the defective nozzle should eject ink. The volumes of the cyan, magenta and yellow inks that are ejected are set to effectively compensate for the missing black dot.