PURPOSE: To lessen the number of times for trial printing, carry out proper judgment for color difference, and carry out proper color matching employing scales for color matching which have at least one representative value or more of concentrations in a concentration histogram of an image to be printed and of which the representative values of concentrations are at least one or more selected from among the mode, the median, and the average values.

CONSTITUTION: A printed matter 2 is like a continuous strip and colored with three colors; a unit U1, a unit U2, and a unit U3; and a scale 1a, a scale 1b, a scale 1c for color matching are formed for each color in a blank space 4 of an image part 3. Each scale has two concentrations. That is, the scale 1a has scales 111, 121, the scale 1b has scales 112, 122, and the scale 1c has scales 113, 123 and the scales are selected from among representative values of a concentration histogram. In the concentration histogram, MO stands for the mode (the most frequent value), ME for the median (the central value) which is the center between the maximum and the minimum of the image concentration, and AV for the average value, which is the average value of all of the concentrations of an image. At least one of the representative values among these values is employed.