The present invention provides an image processing method and image processing device for performing image processing, based on image data and/or drawing instructions, on a page layout which employs process colors inputted from an image processing terminal. The image processing method includes: (a) specifying a color substitution of one of the process colors for the image data and/or drawing instructions; (b) instructing addition of a paper color, including color information, to the whole area of the page layout; and (c) performing the color substitution by adding the color information of the paper color to color information of a substitution color which is being substituted for the process color specified by the color substitution.