Herein disclosed is an optical modulator, comprising: a substrate (1) having an electro-optic effect; an optical waveguide (3) formed in the substrate; a traveling wave electrode (4) including a center electrode (4a) and ground electrodes (4b, 4c) to have a high frequency electric signal applied thereto, the traveling wave electrode and the optical waveguide collectively forming a high frequency interaction portion (20) to have the incident light phase modulated under the condition that the high frequency electric signal is applied to the traveling wave electrode; and bias electrodes each including a center electrode (22a, 23a) and ground electrodes (22b, 22c, 23b, 23c) to have a bias voltage applied thereto, each of the bias electrodes and the optical waveguide collectively forming a bias voltage interaction portion (19, 21) to have the incident light phase modulated under the condition that the bias voltage is applied to the bias electrode, in which the traveling wave electrode and the bias electrodes are extended in a propagation direction of the incident light with the traveling wave electrode (20) positioned between the bias electrodes (19, 21).