An image processing method comprising: an abnormal recording element information acquisition step of acquiring abnormal recording element information with respect to an abnormal recording element which cannot eject ink or which can eject ink but has an abnormality of an ink flying direction or an ink ejection amount [page 5, l. 37 to 39]; a mask processing step of masking a pixel group to be formed by the abnormal recording element based on the acquired abnormal recording element information to exclude the pixel group from quantization processing [page 6, l. 13 to 16]; a pixel value change step of raising [page 7, l. 16, last word] pixel values of pixels (29A, 29B) formed by normal recording elements (25A, 25B) in the periphery of the abnormal recording element [page 7, l. 9 to 12]; an input image data conversion step of converting input image data such that pixels other than the masked pixel group are shifted in column units of the input image data [Fig. 6] to remove the masked pixel group from the input image data and the excluded pixel is compensated for; a quantization processing step of applying quantization processing to convert the converted input image data to image data having a gradation number less than a gradation number of the converted input image data; and a recording element assignment step of assigning each pixel column in the converted and quantized input image data to a normal recording element excluding the abnormal recording element by again shifting pixel columns in the converted and quantized input image data in column units in opposite direction compared to the input image data conversion step for assignment to a normal recording elements [page 11, l. 12, 13]. an abnormal recording element information acquisition step of acquiring abnormal recording element information with respect to an abnormal recording element which cannot eject ink or which can eject ink but has an abnormality of an ink flying direction or an ink ejection amount [page 5, l. 37 to 39]; a mask processing step of masking a pixel group to be formed by the abnormal recording element based on the acquired abnormal recording element information to exclude the pixel group from quantization processing [page 6, l. 13 to 16]; a pixel value change step of raising [page 7, l. 16, last word] pixel values of pixels (29A, 29B) formed by normal recording elements (25A, 25B) in the periphery of the abnormal recording element [page 7, l. 9 to 12]; an input image data conversion step of converting input image data such that pixels other than the masked pixel group are shifted in column units of the input image data [Fig. 6] to remove the masked pixel group from the input image data and the excluded pixel is compensated for; a quantization processing step of applying quantization processing to convert the converted input image data to image data having a gradation number less than a gradation number of the converted input image data; and a recording element assignment step of assigning each pixel column in the converted and quantized input image data to a normal recording element excluding the abnormal recording element by again shifting pixel columns in the converted and quantized input image data in column units in opposite direction compared to the input image data conversion step for assignment to a normal recording elements [page 11, l. 12, 13].