To favorably reproduce gray even when cubic interpolation is used for interpolation calculation.

When creating a color conversion table registering color conversion values at grid points corresponding to vertices of cube areas obtained by dividing an RGB color space into eight areas in RGB directions, in a cube area including an achromatic axis, color conversion values at three grid points adjacent to grid points A, G on the achromatic axis in the RGB directions (three grid points B, D, E adjacent to the grid point A and three grid points C, F, H adjacent to the grid point G) are adjusted so that an average value of the color conversion values of the three grid points can be close to color conversion values at intersections and of a plane passing through the three grid points and the achromatic axis. According to the method, a color conversion table can be created which favorably reproduces gray even when cube interpolation is used for interpolation calculation.