An optical transmitter according to an exemplary aspect of the present invention is an optical transmitter that includes a variable-wavelength light source and a modulator for modulating and outputting the output light of the variable-wavelength light source in accordance with data to be transmitted, wherein the optical transmitter includes a control unit for varying the bias voltage of the modulator based on the light output power of the modulator to make feedback control of the light output power of the modulator during switching of the output wavelength of the variable-wavelength light source.