To provide sufficient strength and flexural rigidity even if a pipe is made of soft material and axial grooves are substantially prevented from being formed by fitting divided circular rings having inside edges in the radial direction so as to surround the end parts of pipes to be fastened.

The shaft ends of a gasket 15 are formed with sealing edges 16, 17 projecting inside, and the outside of pipes 3 are pressed in the fastened state. A metallic plate ring 18 is arranged inside the intermediate part of the gasket 15. The material of the gasket 15 is not crushed between the end parts of the pipes 3 in the condition being fastened by the ring 18. A cutline between both end parts of a circular casing 1 are connected together with bridges contacted with the outer circumference of the gasket 15. Rings 12 containing teeth 13 are slanted by about 45° to pipes, hence when high inner pressure is applied to the pipe 3, the pipes 3 are prevented from being separated from each other by the teeth 13, and because the pipes are apt to rise up, the teeth 13 are more deeply penetrated in the pipe material to avoid formation of axial grooves on the pipes 3.