An optical switch element (1) for switching an optical path (2) comprises
a fixed reflection element (4), which requires strict preciseness in
positioning and angle-setting, and a movable optical path parallel
displacement element (3A), which permits relaxed preciseness in
positioning and angle-setting. When the movable optical path parallel
displacement element is not present in the optical path, light goes
straight, and when the optical path displacement element is inserted into
the optical path, light running in the optical path is displaced in
parallel, inputted into the fixed reflection element, and bent by the
fixed reflection element.