To provide a traveling-wave-type optical modulator and a method of adjusting the same, in which an occurrence of a jitter can be suppressed when an optical modulator is driven by using a driver, and, in particular, to provide a traveling-wave-type optical modulator and a method of adjusting the same, in which a degree of freedom is improved when combining the driver and the traveling-wave-type optical modulator and an occurrence of the jitter can be effectively suppressed even after combining the driver and the traveling-wave-type optical modulator.With reference to a traveling-wave-type optical modulator which includes a substrate having an electrooptic effect, an optical waveguide formed on the substrate, and a modulation electrode performing modulation control on a light wave propagating through the optical waveguide, a driver for controlling driving of the traveling-wave-type optical modulator is connected to the traveling-wave-type optical modulator, and a frequency characteristic (b) of an electro/optical conversion response of the traveling-wave-type optical modulator is adjusted so as to correct a frequency characteristic (a) of a gain of the driver. Preferably, in the adjustment of the frequency characteristic of the electro/optical conversion response, at least one of an impedance value of the modulation electrode or an impedance value of the resistor of termination is adjusted.