Chip-based biosensor arrays for label-free and high-throughput detection were fabricated and tested. The sensor array was composed of a 150-nm-thick, 50-nm-gap, and 600-nm-period gold nanoslits. Each array size was . A transverse-magnetic polarized wave in these metallic nanostructures generated resonant surface plasmons at a wavelength of about in a water environment. Using the resonant wavelength shift in the nanoslit array, we achieved detection sensitivity up to per refractive index unit, about 1.7 times larger than that reported on an array of nanoholes. An antigen–antibody interaction experiment in an aqueous environment verified the sensitivity in a surface binding event.