PURPOSE: To make peripheral welding, cooling and pressure welding in end stopper welding of fuel element continuously by making a cooling chamber of He gas atmosphere communicate with a peripheral welding section and pressure welding section of a welding chamber through outlet and inlet ports respectively.

CONSTITUTION: Fuel element H preliminarily cooled in an air lock chamber is led from an inlet port 26 to a secondary cooling chamber 6 of He gas atmosphere and advanced to a position D in a barrel 25. In the meantime, it is cooled to a specified temperature. Then it is sent from outlet and inlet ports 28 to the peripheal welding section 34 of a welding chamber 33, and after peripheral end stopper welding, pulled back to the cooling chamber 6. The fuel element (h) advances to the position of the second exit port 29 while being cooled by rotation of the barrel 25, and sent to the pressure welding section of the welding chamber 33 and pressure-welded. Then, it is returned to the cooling chamber 6 again, and after cooling, sent to the air lock chamber 51 for discharge. Tact time can be shortened and its throughput can be increased without strain by this device.