PURPOSE: To improve a power efficiency and a sealing property by a method wherein a pulse current is applied directly between a metal cap and a metal ring when they are electrically welded to each other.

CONSTITUTION: An IC is mounted on a ceramic substrate 4 to which a metal ring 3 has been fixed and a metal cap 2 is put on the metal ring 3. Roller electrodes 1 are provided pressing the metal cap 2, a pulse current source 5 is connected between the roller electrodes 1 and the metal ring 3, and a pulse current is made to flow. When the wiring has taken place as mentioned above, the pulse current is made to flow from an electrode of the pulse current source 5 to the other electrode via the roller electrodes 1, the metal cap 2, and the metal ring 3, so that an invalid electrode is eliminated. By this setup, a power efficiency and a sealing property can be improved.