To provide a technique which prevents a discriminating medium from being reused by making a history trying to peel off the discriminating medium fixed on a body to be stuck with a pressure-sensitive adhesive remain. In a discriminating medium 3 which uses a cholesteric liquid crystal layer 22 and can be optically discriminated, a black pressure-sensitive adhesive layer 24 is made to be a structure into which an organic solvent is easily permeated, and a microcapsule-containing layer 32 containing microcapsules 1 and 2 is provided by bringing it into contact with there. The microcapsules 1 and2 are each composed of a material being soluble in an organic solvent which dissolves the black pressure-sensitive adhesive layer 24 and encapsulate respectively dyes and color developing agents therein. When the organic solvent is permeated into the black pressure-sensitive adhesive layer 24 to peel off the discriminating medium 3, the microcapsules are broken and the dyes and the color developing agents are mixed to develop a color. An unfair reuse of the discriminating medium 3 is prevented thereby.