An optical device formed on a substrate comprises: plural fiber channels formed in the top surface of the substrate; a mirror to be pushed into and pulled out of an optical path between optical fibers disposed in the fiber channels; a movable rod carrying at one end the mirror; a comb-type electrostatic actuator disposed in association with the intermediate portion of the movable rod, for moving the movable rod lengthwise thereof; and plural support beams disposed near the one and the other end of the movable rod on both sides of the point of application of driving force by the comb-type electrostatic actuator, for movably supporting the movable rod. The support beams support the movable rod at positions having line symmetry with respect to a center line parallel to the lengthwise direction of the movable rod, and points of supporting the movable rod by the plural support beams are symmetrical with respect to the point of application of the driving force by the comb-type electrostatic actuator. Even if the driving force by the comb-type electrostatic actuator contains a vector component of a direction different from the desired one in which to drive the movable rod, it is possible to suppress movement of the movable rod in other directions than the desired one to drive the movable rod.