An optical switch comprises a prism for changing the direction of travel of incident light to be directed toward a further optical fiber; a switching mirror placed to be insertable and removable into and from between a lens block and the prism; and an actuator for driving the mirror, in which incident and emitting optical fibers are placed in the same facing, i.e. on one surface side, of the device body. This structure makes it possible for components to be used in common and integrated, and for the coupling surfaces between the lens block and the optical fibers to be gathered together in one place, thereby enabling cost reduction and size reduction.