1. A colorimetric method of measuring a color printed on a printing material containing a fluorescent brightener under a predetermined viewing illuminant, using a computer to perform the steps of: an acquisition step of acquiring a first color patch and second color patch specified to match each other in appearance when a plurality of color patches formed on a printing material containing the fluorescent brightener and a plurality of color patches formed on a printing material free from the fluorescent brightener are compared under the predetermined viewing illuminant; a measurement step of performing colorimetric processing using spectrophotometric colorimetry for the first color patch and the second color patch to obtain a first colorimetric value and a second colorimetric value; and a colorimetric value correction step of correcting a colorimetric value output from a spectrophotometric colorimeter based on a relationship between the first colorimetric value and the second colorimetric value.