An image processing apparatus including: a halftone processing unit configured to generate halftone image data represented by a halftone dot corresponding to a density value by performing halftone processing using a dither matrix for input image data; a phase change processing unit configured to correct a deviation of a laser beam scan line that is used in forming an image in accordance with the input image data on a printing medium by performing phase change processing to shift the phase of a pixel in the halftone image data in a sub scanning direction; and a pseudo high-resolution processing unit configured to convert the halftone image data after the phase change processing into halftone image data with a lower resolution by performing pseudo high-resolution processing, and in the dither matrix, threshold values are arranged so that the number of pixels in the sub scanning direction, which make up the halftone dot, is always even.