A reflective optical switch comprises an input/output port portion; a polarization separator/combiner for separating lights in the same optical path and combining lights in different optical paths; a Faraday rotation angle changer; a polarization rotator for changing the relationship in polarizing direction between lights in different optical paths; a birefringence element for optical path control for controlling optical path shift in response to polarizing direction; and a polarization rotating reflector for rotating polarizing direction 90 degrees on forward and return paths. The input/output port portion, the polarization separator/combiner, the Faraday rotation angle changer, the polarization rotator, the birefringence element for optical path control, and the polarization rotating reflector are arranged along the optical path, and the Faraday rotation angle changer includes a Faraday element and an electromagnet for controlling 90-degree change in polarizing direction of transmitted light thereof.