An image processing apparatus which performs a quantization process to multivalued image data consisting of plural density components including at least a first density component and a second density component different from the first density component, and outputs a quantization result of three values or more, comprising: density component accumulated value calculation means for calculating a first density component accumulated value obtained by accumulating a density value of the first density component in an objective pixel of a multivalued image represented by the multivalued image data and a first density component error value diffused from an adjacent pixel of the objective pixel, and a second density component accumulated value obtained by accumulating a density value of the second density component in the objective pixel and a second density component error value diffused from the adjacent pixel of the objective pixel; first quantization result calculation means for calculating a first quantization result based on a threshold corresponding to the second density component accumulated value and the first density component accumulated value in a case where the first density component accumulated value is smaller than a predetermined first quantization method determination threshold, and calculating the first quantization result based on the first density component accumulated value and not the second density component accumulated value in a case where the first density component accumulated value is equal to or larger than the predetermined first quantization method determination threshold; first error diffusion means for calculating an error amount of the first density component based on the first quantization result and diffusing the calculated error amount to a peripheral pixel; second quantization result calculation means for calculating a second quantization result based on a threshold corresponding to the first density component accumulated value and the second density component accumulated value in a case where the second density component accumulated value is smaller than a predetermined second quantization method determination threshold, and calculating the second quantization result based on the second density component accumulated value and not the first density component accumulated value in a case where the second density component accumulated value is equal to or larger than the predetermined second quantization method determination threshold; second error diffusion means for calculating an error amount of the second density component based on the second quantization result and diffusing the calculated error amount to the peripheral pixel. density component accumulated value calculation means for calculating a first density component accumulated value obtained by accumulating a density value of the first density component in an objective pixel of a multivalued image represented by the multivalued image data and a first density component error value diffused from an adjacent pixel of the objective pixel, and a second density component accumulated value obtained by accumulating a density value of the second density component in the objective pixel and a second density component error value diffused from the adjacent pixel of the objective pixel; first quantization result calculation means for calculating a first quantization result based on a threshold corresponding to the second density component accumulated value and the first density component accumulated value in a case where the first density component accumulated value is smaller than a predetermined first quantization method determination threshold, and calculating the first quantization result based on the first density component accumulated value and not the second density component accumulated value in a case where the first density component accumulated value is equal to or larger than the predetermined first quantization method determination threshold; first error diffusion means for calculating an error amount of the first density component based on the first quantization result and diffusing the calculated error amount to a peripheral pixel; second quantization result calculation means for calculating a second quantization result based on a threshold corresponding to the first density component accumulated value and the second density component accumulated value in a case where the second density component accumulated value is smaller than a predetermined second quantization method determination threshold, and calculating the second quantization result based on the second density component accumulated value and not the first density component accumulated value in a case where the second density component accumulated value is equal to or larger than the predetermined second quantization method determination threshold; second error diffusion means for calculating an error amount of the second density component based on the second quantization result and diffusing the calculated error amount to the peripheral pixel.