There is provided an optical device including a substrate having an electro-optical effect, a plurality of optical modulators including bias electrodes to which a bias voltage is applied so as to generate an electric field from one of the bias electrodes to another of the bias electrodes, and the bias electrodes of the optical modulators being disposed above the substrate, and a partition conductor to reduce influence of the electric field from the bias electrode of a first optical modulator to an optical waveguide of a second optical modulator, the partition conductor being disposed above the substrate.