<p>An optical transmitter includes: a data generating unit (6) configured to generate a plurality of modulating signals; a driver (9) configured to amplify the plurality of modulating signals generated by the data generating unit (6); a phase shifter (7) configured to control a phase of at least one signal among the plurality of modulating signals to be input to the driver (9); a plurality of optical modulators (2) connected in series to each other, and configured to modulate an optical signal on a basis of each of the modulating signals amplified by the driver (9); an optical coupler (3) configured to branch the optical signal modulated by the optical modulator (2) arranged at a last stage in the series; a photodiode (4) configured to detect the optical signal branched by the optical coupler (2) and converts the optical signal into an electric signal; and a phase control unit (5a) configured to control an amount of phase control of the phase shifter (7) to maximize an intensity of the electric signal converted by the photodiode (4).</p>
