PURPOSE: To provide the optical switch which is capable of completely seal a matching agent, such as silicone oil and preventing the generation of stains and air bubbles of the matching agent occurring in the mechanical contact and wear of a driving part and eliminates the need for immersing a sensor for position adjustment, etc., into the matching agent.

CONSTITUTION: The end of a stationary side optical fiber 3 and the end of a moving side optical fiber 4 are immersed into the refractive index matching agent 1 in a liquid form sealed and packed into a matching agent vessel 21. A moving member 5 which is disposed in this matching agent vessel 21 and moves the end of the moving side optical fiber 4 is sealed by an elastic thin film 51 disposed between this member and the matching agent vessel 21 side. The matching agent 1 is sealed in the matching agent vessel 21 over a long period of time, by which the leakage of the matching agent to the outside is completely prevented.