An optical device includes a rib optical waveguide that is a thin-film lithium niobate (LN) crystal formed of a thin-film LN substrate, and a buffer layer that is laminated on the optical waveguide. The optical device further includes an electrode that is laminated on the buffer layer, and sub electrodes that are arranged parallel to the electrode on the buffer layer, and attract a charge in the optical waveguide in accordance with electrification.