A gold-deposited optical fiber sensor system based on surface plasmon resonance (SPR) was developed for optical measurement of neuronal activity. To enhance the sensitivity of localized SPR and to make a precise and safe contact with the cellular membrane, we designed a tapered optical probe of 1m diameter at the tip of the fiber. By wet etching and gold evaporating processes, pencil-shaped optical probes were successfully fabricated. The SPR system with the sharp optical probe was integrated with a conventional patch clamping system to realize a simultaneous optical and electrical recording on a single neuron. Although the shape of optical signal is not clear due to tiny change of intrinsic optical properties on the neuron, optical and electrical signals were simultaneously changed by capsaicin stimulation. Furthermore, our designed fiber probe can be applicable to localized optical stimulation as well as in vivo optical neuroprosthetic devices.