PURPOSE: To stop any possible leakage easily and safely in a short time by crushing the upstream side of a leaking part in a pipeline, making this crushed part form a passage successively into narrowness in the downstream direction, and decompressing a fluid by this crushed part, then attaching a closing member to the pipeline, finally stopping any leakage of the fluid.

CONSTITUTION: When a leak has happened in a branch pipe 2d, by way of example, installed in a main pipe 1, this branch pipe 2d is crushed at its A position from the outside, forming a crushed part 12a which is made up over plural stages at the upstream side of the leaked part of a pipeline, and each of four crushed parts 12a-12d is contracted as far as more than for example, 50%, 70%, 80-90%, 95% in each inner diameter, thus they are formed into narrowness successively in proportion as going in the downstream direction. A fluid is decompressed by an orifice function by means of these crushed parts, and a valve 5 of a closing member is installed at the upstream side of the leaked part, thereby stopping any leakage of the fluid. In consequence, sealing repair can be easily done in a short time without incurring any production loss, as leaving the fluid live intact.