A composition for diagnosing amyloid-related diseases, which comprises a flavone derivative, a chalcone derivative, a styrylchromone derivative, or a coumarin derivative, is provided. These compounds have high binding specificity to an amyloid β protein, high permeability to a blood-brain barrier, and ability to rapidly disappear from sites other than cerebral senile plaque. Accordingly, the composition of the present invention using these compounds enables the diagnosis of amyloid-related diseases with high precision.