An optical transmission apparatus (100) includes an optical transmitter (200) including an optical modulator (220) and an observation optical modulator (230) that attenuate optical power of input continuous wave light by an electro-absorption effect and output the continuous wave light. The optical modulator (220) performs pulse amplitude modulation on the continuous wave light and outputs the optical signal. The apparatus also includes: a bias voltage generation unit (350) that generates a direct-current bias voltage and outputs the direct-current bias voltage to the optical modulator (220) and the observation optical modulator (230); a modulation signal generation unit (360) that generates an electrical signal for pulse amplitude modulation and outputs the electrical signal to the optical modulator (220); and a bias voltage control unit (340) that instructs the bias voltage generation unit (350) to adjust the direct-current bias voltage on the basis of an absorption amount of optical power in the optical modulator (220) and an absorption amount of optical power in the observation optical modulator (230).