Alzheimer's disease is a progressive neurodegenerative disorder that is characterized by the deposition of beta-amyloid (Abeta) peptide and the formation of neurofibrillary tangles in neurons. The Abeta peptide is a key molecule in the pathogenesis of Alzheimer's disease and an important marker for early diagnosis. Surface-enhanced Raman scattering (SERS) has recently been attracting keen interest in various fields such as for biosensors or immunoassays. In this study, gold nanoparticles (Au NPs) were electrochemically deposited on an indium tin oxide (ITO) substrate at different heights. Abeta antibodies were immobilized on the Au-NP-coated ITO substrate, after which the interactions between the antigen and the antibody were determined via SERS spectroscopy. The SERS responses were strongest at the Au NP array height of 91 nm, with a good linear relationship that corresponded to the change in the concentration of the antigen. This Au-NP-array-mediated SERS can be applied with a highly sensitive immunodetection biosensor.