A specifying section specifies in printing data a first dot position at which a defective nozzle discharges an ink droplet to print the ink droplet on a medium when the defective nozzle is not defective, but is normal, and specifies in printing data a second dot position different from the first dot position based on priority information in which priority is set for each pixel. A data correcting section corrects the printing data. The collecting corresponds to allocating an amount of ink of the first dot position to the second dot position. When the first dot position at which the ink droplet is provided to the medium if the defective nozzle is not defective is specified, a neighboring second dot position different from the first dot position is specified based on the preset priority information, and the data correcting section corrects the printing data so as to allocate the amount of ink to the second dot position based on the mount of ink of the first dot position.