Interpolated image data is generated from image-sensing data according to the color characteristic of an object. A color filter that has a strong correlation with the color characteristic of an object in image-sensing data captured by an image sensing device having a color filter array in which filters of a plurality of colors are arranged is determined. Interpolated image data of a color component corresponding to the determined color filter is generated by using the pixel values of the image-sensing data corresponding to the color filter. Interpolated image data of the color component corresponding to each of color filters different from the determined color filter is generated by using the generated interpolated image data and the pixel values of the image-sensing data corresponding to each of the color filters different from the determined color filter.