PURPOSE: To obtain an input/output terminal holder of a fiber for transmission which is highly resistant to heat and is easily attachable and detachable by utilizing the shape changes of shape memory alloys to fix the input/output end of the fiber for transmission to a sleeve, etc.

CONSTITUTION: Shape memory alloy rings 8aW8d are used for the input/output terminal holder of the fiber for transmission. A protective tube 3 of the fiber is fixed to the sleeve 2 by the shape memory alloy 8a. The input/output end 1 of the fiber is fixed via a fiber protective film 9 formed thereon by the shape memory alloy ring 8b. The sleeve 2 and a cap 5 are fixed by the shape memory alloy ring 8c. a window part 7 for laser light input/output is retained to the cap 5 by a window retaining ring 10 and is fixed by the shape memory alloy ring 8d. The shapes of the fixing members at the time of detaching and fixing are changed simply by changing the temp. thereof, by which the fixing members are easily attached and detached. The attachment and detachment of the input/ output and 1 of the fiber are thus permitted without damaging said end in spit of heating.