Abstract: A method for measuring the concentration of adhesive on the surface of a coating layer which has the steps of irradiating the surface of the coating layer with an ultraviolet ray of the highest peak absorption wavelength of the adhesive, ultraviolet ray of shorter wavelength and ultraviolet ray of longer wavelength, photoelectrically converting the reflected rays and further comparing to calculate them. Thus, this method can be used to measure the concentration of adhesive on the surface of a coating layer and the flat surface distribution of the adhesive by fundamentally measuring with ultraviolet rays. The method is of high reliability despite the presence of gloss or the like.