PURPOSE: To improve a joining strength and to reduce the cost by forming a tapered faucet, etc., at the end part of a pipe stock, inserting the pipe stock of the other part as well by interposing an elastic gasket ring, then performing the joining on the pipe by approaching a split die tool.

CONSTITUTION: A faucet part 3, tapered faucet part 4, cylindrical part 5 and inward bending end part 6 are formed with the diameter expanding of the end part of the pipe stock 1 of one part. The pipe stock 2 of the counterpart side is inserted into the pipe stock 1 by interposing an elastic gasket ring 7. The split die tools 9, 10 equipped with a taper forming part 8 are arranged on the outer peripheral face of the pipe stocks 1, 2 with their opposition and approached along the pipe shaft. In this case, the taper forming part 8 strongly presses the cylindrical part 5 to be plastically deformed in a reverse tapered part 5A and the bend end part 6 is bitten into the pipe stock 2. With this method, the joining strength of the pipe stocks 1, 2 is improved and the joining cost is reduced as well because of using the gasket ring 7 only.