An image processing apparatus includes (i) a repulsive force generating section for setting repulsive force values RVa and RVu of a quantized pixel according to an output pixel value of the quantized pixel, (ii) a repulsive force calculating section for calculating a repulsive force value RVC to be used in quantizing a quantization-target pixel by attenuating, according to a distance between the quantized pixel and the quantization-target pixel, the repulsive force values RVa and RVu set for the quantized pixel; and (iii) a threshold value correcting section for correcting a threshold value T used in quantizing the quantization-target pixel according to the repulsive force value RVC. This makes it possible to prevent an increase in the number of processing steps and amount of processing when an image is processed with an error diffusion method. At the same time, it is possible to prevent decrease in image uniformity and formation of a pattern unique to the error diffusion method.