An image processing apparatus comprises: a N-valued conversion unit that converts color component values of plural colors comprised in pixels constituting input image data into N-valued values in a unit of color based on threshold values of the plural colors; a dither matrix storage unit that stores dither matrixes in which one dither pattern or one kind of dither pattern is repeated in a unit of dither pattern; a counter that holds a value specifying a readout position of a row of each dither matrix; and a readout unit that reads out the threshold value of each color used from plural kinds of dither matrixes based on the values from the counter, wherein the number of threshold values constituting a row of the plural kinds of dither matrixes is a common multiple of the number of threshold values constituting a row of the plural kinds of dither patterns.