An image processing device includes a pre-processing unit, an adder, a quantization unit, a post-processing unit and a surrounding error calculating unit. The pre-processing unit calculates an average pixel value of an aggregated pixel formed of a plurality of adjacent pixels for input image data. The adder calculates a correction average pixel value by adding a correction error value to an average pixel value of a target aggregated pixel to be a processing object. The quantization unit carries out a quantization processing of the correction average pixel value at a quantization level of a prescribed number. The post-processing unit divides the aggregated pixel into a plurality of pixels and allocates a pixel value corresponding to the quantization level to each of the divided pixels. The surrounding error calculating unit calculates a correction error value for processing a surrounding target aggregated pixel in accordance with a quantization error generated in the quantization processing.