PURPOSE: To facilitate the formation of a switch matrix by placing states of up to specific order in a total reflecting state and the succeeding states in a transmission state, and outputting input light switch passes through the total reflecting part from the (M)th output port when the refractive index at the time of control in N stages is set to the (M)th stage.

CONSTITUTION: Input light 1 is inputted to the switch through an input port 2 and then reflected totally by total reflecting parts 3W5 in order to obtain output light 10 through an output port 9. What state the total reflecting parts 3W5 are in is indicated at stages (1)W(4) of refractive index control and the output light is obtained from the input light through one of output ports 6W9 according to a control stage. When the refractive index is varied to a control stage 2 from the control stage 4, and then the input light 1 is reflected totally by the total reflecting part 3 and not reflected totally by the total reflecting part 4, so that the output light is obtained from the output port 7. The refractive index is controlled by electrooptic effect and carrier injection effect, etc., and an electrode is provided to the total reflection parts in common and a voltage of several V is impressed in either method to facilitate the control. Consequently, the number of the output ports is ≥3 and the formation of the switch matrix is facilitated.