In an optical modulator, an intermediate substrate is provided separate from a main substrate on which a plurality of optical modulation sections are provided in parallel, and signal lines corresponding to the optical modulation sections are formed on the intermediate substrate. The signal lines are connected to signal electrodes corresponding to the main substrate, and have electrical lengths that are different from each other. Furthermore, the propagation loss per unit length in the signal lines on the intermediate substrate is preferably less than the propagation loss per unit length in the signal electrodes on the main substrate. As a result, even if a plurality of optical modulation sections are arranged in parallel, and the input ends of the signal electrodes of the optical modulation sections are arranged side by side on one side face of the substrate, synchronized modulation light of a low noise at a wide band width can be output from the optical modulation sections.