PURPOSE: To miniaturize it installably in the inner part of a joint by providing a valve body in contact with a valve seat installed in a fluid circuit and a seal member, closing an outlet of a fluid passage, both in the valve body, and exhausting a fluid at the side of high pressure by way of a fluid exhaust passage after the valve seat part is closed when the fluid circuit is interrupted.

CONSTITUTION: A safety valve consists of a valve body and an O-ring 26 attached to the outer circumference. This valve body is composed of a stepped cylindrical guide part 51, a disklike contact part 52, a cylindrical sealant setting part 56, a cylindrical projecting part 58. A joint is constituted of a nipple 10 and a coupler 30, and the safety valve 50 opening or closing a flow passage is installed in the inner part. This valve 50 comes into contact with a valve seat 17 in a nipple body 11, closing the flow passage, and it is sealed by another O-ring 18, so that it is able to open or close a fluid exhaust passage by dint of a pressure differential between ports of this exhaust passage being produced at time of something trouble.