An image processing apparatus comprising: a region extraction unit configured to extract a conversion region from input image data, the conversion region being a region of human skin in the input image data; a color information acquisition unit configured to acquire color components of pixels included in the conversion region and to calculate a three-dimensional tone function from the color components as color information, wherein the tone function is an approximation function obtained by using a regression analysis so that distances to data groups of pixels of the color components are minimum, and illustratable as a solid curve in a three-dimensional graph; a target color information acquisition unit configured to acquire a target function having the same data format as the tone function, as target color information, which is a target of conversion for the color information, wherein the target color information acquisition unit is configured to acquire at least first target color information and second target color information; a conversion unit configured to: generate first conversion information based on the color information and the first target color information, generate second conversion information based on the color information and the second target color information, convert the input image data based on the first conversion information to generate first converted image data, and convert the input image data based on the second conversion information to generate second converted image data; a display and input unit configured to display the input image data and the first and second converted image data (A; B), and to receive an input of a final conversion target, which is a final target of conversion for the color information; and a final conversion unit configured to generate final conversion information based on the final conversion target, and to convert the input image data based on the final conversion information, to generate final image data. a region extraction unit configured to extract a conversion region from input image data, the conversion region being a region of human skin in the input image data; a color information acquisition unit configured to acquire color components of pixels included in the conversion region and to calculate a three-dimensional tone function from the color components as color information, wherein the tone function is an approximation function obtained by using a regression analysis so that distances to data groups of pixels of the color components are minimum, and illustratable as a solid curve in a three-dimensional graph; a target color information acquisition unit configured to acquire a target function having the same data format as the tone function, as target color information, which is a target of conversion for the color information, wherein the target color information acquisition unit is configured to acquire at least first target color information and second target color information; a conversion unit configured to: generate first conversion information based on the color information and the first target color information, generate second conversion information based on the color information and the second target color information, convert the input image data based on the first conversion information to generate first converted image data, and convert the input image data based on the second conversion information to generate second converted image data; a display and input unit configured to display the input image data and the first and second converted image data (A; B), and to receive an input of a final conversion target, which is a final target of conversion for the color information; and a final conversion unit configured to generate final conversion information based on the final conversion target, and to convert the input image data based on the final conversion information, to generate final image data.