To reduce the amount of a leaked fluid by automatically stopping leakage from a packing, resulting in decreasing the damage probability of a living being or a body due to the leaked fluid, and to reduce a period of time and labor for disposing the leaked fluid, and further to eliminate a danger in leakage-stopping work.

Provided are a packing 16 included in the gap of a shaft 12- movably inserted hole 10a in a valve wall 10 and for preventing fluid communication through the gap, a packing support member 10b and a packing gland member 18 for preventing the packing from drop from one side to the other side through the gap, and a temperature-change deformation member 20 for preventing fluid leakage through the gap by increasing pressing force against the packing owing to deformation encountered by receiving the influence of the temperature of the fluid leaked to the packing.