The present invention relates to a high-frequency signal transmitting optical module which can easily realize a high-frequency signal transmission by use of a semiconductor optical device to which a highly versatile metal can package has been applied. In the high-frequency signal transmitting optical module, after fixing, to a rear surface of a stem of the metal can package, fixing portions of the linear outer leads by laser welding, the end portions of the outer leads are bent. By this, the outer leads can be easily attached to the semiconductor optical device. On both sides of the respective lead pins of the semiconductor optical device, since the outer leads extending along these are attached to the rear surface of the stem, ground regions are continuously provided on both sides of the respective lead pins by the stem and respective outer leads, whereby TEM wave transmission lines are formed. Accordingly, high-frequency signals can be transmitted to the semiconductor optical device.