184Multifunctional devices have also be proposed to perform optical stimulation and electric neural measurement simultaneously. Optrode is a group of devices consisting of light-guide structure and electrode for electric measurement 7)~9) . In most cases, one or several light-guides are implemented onto an electrode array. Light is deliverd to the optorode using optical fibers. The optical fiber and wire harness prevent to use the optorodes in freely moving situations. A device with capabilities of local light stimulation and electric neural measurement with fexible interconnection is required for freely-moving situations. In this work, we propose a CMOS-based optoelectronic device which is capable of not only stimulating the neural system with integrated micro light source array, Abstract A CMOS-based optoelectronic device is proposed for on-chip neural stimulation and observation with optogenetic methodology. The device is capable of local light delivery for stimulation and electrical neural signal recording. The device consists of an array of InGaN light emitting diodes (LEDs) and Au stacked bump electrodes integrated on a CMOS image sensor. Capabilities of on-chip light stimulation and signal recordingwere quantitatively characterized. We have also confirmed that neuron-like cells can be cultured on the surface of the device.