This presents an image processing apparatus and an image processing method which print and output image data subjected to halftone processing with an appropriate density characteristic. The image processing apparatus generates a halftone image from a multi-value image using a threshold value arrangement, and generates a difference image between the generated halftone image and a second halftone image having the density characteristic different from that of the generated halftone image. The image processing apparatus stores the generated halftone image and the generated difference image. The image processing apparatus determines the density characteristic for printing the second halftone image, when determining to carry out printing with the density characteristic different from that of the stored halftone image, generates a halftone image by combining the stored difference image according to the determined density characteristic and the stored halftone image, and outputs the combined halftone image for printing.