To provide a high frequency characteristic measuring system capable of measuring various high frequency characteristics, for example, of a communication semiconductor laser, efficiently and highly accurately in a short time without reconnecting a high frequency cable or the like.

This system is equipped with a plurality of signal generators for generating respectively a high-frequency signal for controlling emission of a device (semiconductor laser). A high-frequency relay circuit interposed in a high-frequency signal transmission path for connecting each signal generator to the semiconductor laser is switched, to thereby select the high-frequency signal applied to the semiconductor laser, and an optical path is switched by using an optical channel switch, to thereby introduce selectively a laser beam (output of the device) emitted by the semiconductor laser into a plurality of kinds of optical measuring instruments (measuring control means).