The present invention relates to a nanoplasmonic sensor based on gold nanoparticle to which an antibody or an aptamer binds, the antibody or the aptamer recognizing Aβ 1-40, Aβ 1-42, and τ protein, which are Alzheimer's disease onset markers that are present in blood, and a multi-detection method of Alzheimer's disease using Rayleigh scattering phenomenon and colorimetric assay of the sensor. The present invention has advantages in that it is possible to perform simultaneous multiple detect with respect to various onset markers by using a simple diagnosis method using blood, and sensitivity of diagnosis is improved by using a chaotropic solvent.