This study reports a fiber-optic sensor detecting biomolecule by simultaneously monitoring localized surface plasmon resonance (LSPR) from gold nanoparticles (Au NPs) of ca. $50{pm}5$ nm attached on one end of optical fiber and surface enhanced Raman scattering (SERS) of the reporter molecules adsorbed on the gold surfaces as an additional sensing tool. The sensor was fabricated by immobilizing Au NPs on one end of an optical fiber by chemical reaction. LSPR and SERS signals of the sensor were measured using various refractive indices solutions. Finally, the sensor was applied to observe real-time LSPR sensor-gram and SERS spectra of the reporter molecule of 4-aminothiphenol during the antibody-antigen reaction of interferon-gamma (IFN-${gamma}$) as a proof-concept experiment of biological applications.