PROBLEM TO BE SOLVED: To provide a quantitative method of benzotriazol on a metallic surface which can measure and determine benzotriazol on metallic surfaces such as a metal plate easily and with sensitively.SOLUTION: In a quantitative method of benzotriazol on a surface of a target metal member, following steps are performed sequentially: a pretreatment step of making an organic alkaline solution contact on the surface of the target metal member; a heating step of heating the target metal member after the pretreatment step; and an analysis step of introducing generated materials that the organic alkali contained in the organic alkaline solution and benzotriazol on the surface of the target metal member reacted into a gas chromatograph or a gas chromatograph mass spectrometer, and analyzing it. Because benzotriazole derivatives are generated only by pyrogenetic reaction, benzotriazol on the surface of the target metal member can be determined easily and quickly.
