Abstract: [Problems] To enable convenient and accurate examination of Alzheimer's disease. [Means for Solving Problems] A reaction liquor, which is prepared by mixing an amyloid ? protein with a body fluid collected from a subject and a buffer solution is reacted. After the polymerization of the amyloid ? protein comes to equilibrium, the degree of the amyloid ? protein polymerization is examined. For example, the above-described reaction liquor is mixed with a fluorescent dye after the completion of the reaction and the degree of the color-development of the reaction liquor is detected to thereby examine the degree of the amyloid ? protein polymerization. The fluorescent dye as described above is thioflavin T or its derivative. The body fluid as described above is cerebral fluid, blood or a blood component.