Disclosed is a method for body fluid-based neurodegenerative disease diagnosis through high-sensitive immunoassay of aggregated proteins by photooxidation-induced amplification. The method according to the present disclosure provides an effect of quantitatively analyzing aggregated proteins in the form of oligomers or monomers which are present in trace amounts in a body fluid and measures normal or abnormal protein aggregation by detecting the aggregated proteins in the form of oligomers or monomers with high sensitivity by reaction of antibody-conjugated enzymes selectively bound to the aggregated proteins with substrates and photooxidation-induced amplification, thereby allowing accurate diagnosis of a neurodegenerative disease.