A lead pin (2a,2b) penetrates a metal stem (1). A support block (3) is mounted on the metal stem (1). A dielectric substrate (4) is mounted on a side surface of the support block (3). A signal line (5a,5b) is formed on the dielectric substrate (4). One end of the signal line (5a,5b) is connected to the lead pin (2a,2b). A semiconductor optical modulation device (6) is mounted on the dielectric substrate (4). A conductive wire (8a,8b) connects the other end of the signal line (5a,5b) and the semiconductor optical modulation device (6). The semiconductor optical modulation device (6) includes a plurality of optical modulators (6b,6c) separated from each other.