An optical switch includes an input port (51), a plurality of output ports (52), a switching element (40) for switching light signals from the input port to any one of the output ports, a base (30), and a housing (10). The switching element has a driving device (400), a rotary holder (410) and two reflectors (422, 424). The reflectors are attached to a supporting arm (414) of the rotary holder, and positions of two counterweights (418) are adjustable on two balancing arms (416) to balance the combination rotary holder--reflectors around an axis of rotation. The input port is mounted in a center hole (352) of the base and the output ports are mounted in peripheral holes (354) defined in a circle around the center hole. Rotation of the rotary holder switches light signals from the input port to be output to any one of the output ports.