Abstract: A small-size large-capacity optical switch in which the switch switching control structure is simple and the switch switching efficiency is excellent. A plurality of fiber accommodating grooves (4) are formed on a grooved board (1) and stationary side optical fibers (5) are held and aligned in the fiber accommodating grooves (4) to form a fiber array unit (8). The fiber array units (8) are laminated with a space therebetween. A master fiber (10) is arranged so as to correspond to the fiber array unit (8) of each stage and the master fiber (10) of each stage is supported and secured by a common master fiber supporter (12). Movement of the master fiber supporter (12) is controlled by fiber movement control means (13) only in a direction in which the fiber accommodating grooves (4) are aligned.