To achieve a size-dependent detection sensitivity of spherical nanoparticles, we propose a one-dimensional array of double-bent Au strips as a nanoplasmonic sensor and also as a size-filtering device. Electromagnetic simulations and measured absorbance spectra demonstrate that local plasmonic fields developed at the double-bent Au strips differentiate plasmonic responses for 100 nm- and 200 nm-sized spherical particles. Our results highlight the potential of the double-bent Au strip array as a sensing platform providing size-dependent sensitivity for spherical analytes.