PURPOSE: To easily observe the extent of shifting from a reference position without any hindrance of dark color with reference to even light color, and to perform density control by using a solid printing part without inspection of decoloration and use of a color ball.

CONSTITUTION: A printing estimation mark which consists of a circle or polygon and plural straihgt lines extending radially from the center of the circle or polygon and thrusting through the circle or polygon is used and solid printing parts in respective colors are provided at prescribed positions of this mark to perform estimation. In this figure, the number of printing colors in use are three and three colors 11, 13 and 15 are printed firstly; the printing color 11 shifts from the mark in the reference color 15 as shown by an arrow A in the figure, and the printing color 13, on the other hand, shifts as shown by an arrow B. For this purpose, the printing color 11 to be estimated is shifted as shown by the arrow A and the printing color 13 is shifted as shown by the arrow B, thus correcting the extents of shifting of respective colors from the reference color 15.