An optical switch according to this invention has a planar waveguide in which an optical path is formed. A trench is formed in the upper surface of this planar waveguide. A cantilevered movable member is mounted on the planar waveguide. A comb is formed in the end portion of this movable member. A mirror which intercepts light propagating on the optical path is fixed to the end of the movable member. An electrode opposing the movable member is formed on the planar waveguide. A comb is formed in that portion of this electrode, which opposes the comb of the movable member. The movable member and electrode are connected via a voltage source. When this voltage source generates electrostatic force between the movable member and electrode, the movable member bends, and the mirror moves along the bottom surface of the trench accordingly.