An image processing method and image processing device which carry out color replacement of any color of process colors, by using another process color or a spot color which is not a process color. CMYK values of raster data of a color for which color replacement is designated, among process colors of an image object, are converted by using CMYK values of a replacement color stored in advance, and raster data of the replacement color is generated. Then, this raster data is composed with raster data of a remaining color which is not subjected to color replacement, or raster data of another color replaced in. At this time, color correction is carried out on raster data of remaining process colors.