PURPOSE: To connect satisfactorily the ends of flux-cored wires and to obtain the weld zone which does not affect adversely post-stages by removing the flux at the ends of said wires, inserting an insert material which consists of the same component as the component of the flux and of which the outside circumference is made refractory and butt welding the ends of the wires.

CONSTITUTION: The flux 7 at the ends of two wires for welding formed by packing a flux 7 into a steel pipe sheath 1 is removed to form a cavity part 3. A packing 8 consisting of the same component as the component of the flux 7 is packed into the two cavity parts 3 and further a packing material 2 formed by making the outside circumference of the flux 7 refractory is inserted into one cavity part 3. The other wire 1' is butted to said part. A gap 4 corresponding to the allowance for welding is allowed to remain in this stage. The wires 1, 1' are gripped by stationary electrodes 5, 5' and electricity is conducted thereto to weld the wires by pressurized joining. Burr 6 is formed on the outside surface of the pipe 1 in this stage but is not formed on the inside surface of the pipe 1. The burr 6 is removed by a grinder and the butt welding is completed.