Patent ID: 7666047

Claim:
A method for producing a spark plug including a center electrode, an insulator having an axial hole in an axial direction for holding the center electrode on a front end side of the axial hole, a metal shell for holding the insulator while surrounding the circumference of the insulator, and a ground electrode having one end portion joined to the metal shell, and the other end portion to which a columnar noble metal tip facing the center electrode is welded, wherein the noble metal content in a position far by about 0.05 mm inward a molten portion between the noble metal tip and the other end portion of the ground electrode from a boundary surface between the molten portion and a non-molten portion of the noble metal tip becomes 60% or higher, the method comprising the steps of: resistance-welding a bottom surface of the noble metal tip on a side opposite to a counter surface of the noble metal tip to an inner surface of the other end portion of the ground electrode on a side opposite to the center electrode to thereby form a flange portion having a swollen outer diameter of the noble metal tip in a bottom portion of the noble metal tip; and welding the noble metal tip to the ground electrode in such a manner that a laser beam is applied on the whole circumference of the flange portion of the noble metal tip obliquely at an angle and is directly applied to the side surface of the noble metal tip.