PURPOSE: To simplify working to the gas cutting only and reduce the number of steps by obliquely cutting the base metal joint to form a groove then welding the portions between the base metals on one side of the liner tack-welded between both base metal joints and removing the linear at the time of forming the welded joint by welding of the two base metals.

CONSTITUTION: Diagonal (bevel) cutting is performed from one or both of the base metals 1, 6 to be welded, for example, from both sides at the base metal 1 end, to form a replacement groove 2 of double J groove and a root 3. Next, a required liner 4 formed by the material of the same kind to the base metal 1 or of the kind resembling thereto is tack-welded 5 thereto. Thereafter, the base metal 1 with the liner 4 is aligned to the other base metal 6 and the groove 2 on one side (right side in the figure) is welded, whereby the base metals 1 and 6 are formed into one body. Upon ending of the welding, back chipping is performed until the sound weld metal appears from the groove 2 on left side, whereby the liner 4 is removed. If the welding of the groove 2 on left side is performed after this, the perfect welded joint is made.