An image processing apparatus that converts input image signals indicating an image of n colors, wherein n≧2, including a first color and a second color to output signals corresponding to individual color materials including a first color material and a second color material and that an output device deals with by interpolation processing using a look-up table, the apparatus comprising: a first conversion unit configured to convert the input image signals of the n colors to converted image signals of n colors for each of the color materials by using a one-dimensional first look-up table; and a second conversion unit configured to convert the converted image signals of the n colors corresponding to the color materials converted by the first conversion unit to the output signals corresponding to the color materials by using a three-dimensional second look-up table and the interpolation processing, wherein colors indicated by the n colors are different from colors of the color materials, wherein the first conversion unit converts an input image signal corresponding to the first color to at least a first signal that is a converted image signal corresponding to the first color material and a second signal that is a converted image signal corresponding to the second color material, and converts an input image signal corresponding to the second color to at least a third signal that is a converted image signal corresponding to the first color material and a fourth signal that is a converted image signal corresponding to the second color material, wherein the second conversion unit outputs the output signal corresponding to the first color material in response to the first signal and the third signal and outputs the output signal corresponding to the second color material in response to the second signal and the fourth signal, wherein curves of the color materials defined by the one-dimensional first look-up table differ among the color material kinds, and wherein the first conversion unit performs nonlinear conversion processing for each color material according to linearity of each signal value corresponding to the individual color materials. a first conversion unit configured to convert the input image signals of the n colors to converted image signals of n colors for each of the color materials by using a one-dimensional first look-up table; and a second conversion unit configured to convert the converted image signals of the n colors corresponding to the color materials converted by the first conversion unit to the output signals corresponding to the color materials by using a three-dimensional second look-up table and the interpolation processing, wherein colors indicated by the n colors are different from colors of the color materials, wherein the first conversion unit converts an input image signal corresponding to the first color to at least a first signal that is a converted image signal corresponding to the first color material and a second signal that is a converted image signal corresponding to the second color material, and converts an input image signal corresponding to the second color to at least a third signal that is a converted image signal corresponding to the first color material and a fourth signal that is a converted image signal corresponding to the second color material, wherein the second conversion unit outputs the output signal corresponding to the first color material in response to the first signal and the third signal and outputs the output signal corresponding to the second color material in response to the second signal and the fourth signal, wherein curves of the color materials defined by the one-dimensional first look-up table differ among the color material kinds, and wherein the first conversion unit performs nonlinear conversion processing for each color material according to linearity of each signal value corresponding to the individual color materials.