Abstract: An optical switch having two spherical or elliptical corner-reflecting surfaces provided in a light-conducting member, a shutter to open and close a light path between the corner-reflecting surfaces, and focusing lenses to focus the incident beam from an emitting optical fiber and to focus the emitting beam from the light-conducting member to a primary receiving optical fiber. Because almost all the beam transmitted through the light-conducting member is focused at one point in an air gap in which the shutter moves, the optical switch can transmit the beam with high efficiency without leakage to the outside, and a small stroke of the shutter is sufficient to completely transmit or stop the beam.