Provided is an optical switching system which is capable of being operated at a very high speed in a communication wavelength region and of meeting the various requests at a high grade by the provision of an optical switching system having such a construction that a signal light composed of a light pulse train, and a pulse-like control light synchronous therewith are applied to a light control portion composed of a thin film made of carbon nanotubes to selectively transmit the light pulse train in the signal light through the thin film to form an output signal light and then receiving the output signal light thus formed is received.