An optical modulation device includes a substrate having a principal surface, and electrodes provided on the principal surface of the substrate. The electrodes have end portion regions on the outer edge side of the principal surface of the substrate in a plan view, and planar-view corner portions provided between tip end outer edges which define the tip end shapes of the end portion regions in a first direction and side surface outer edges which define the side surface shapes of the end portion regions in the plan view have chamfered shapes.