Patent ID: 8427038

Claim:
A spark plug comprising: a rod-shaped center electrode extending in an axis direction of the spark plug; a cylindrical insulator having an axial hole formed therein in the axis direction and retaining the center electrode in the axial hole; a cylindrical metal shell disposed on an outer circumference of the insulator; and a ground electrode made of a nickel-based alloy, extending from a front end portion of the metal shell and bent at a substantially middle portion thereof in such a manner as to define a spark gap between a front end portion of the ground electrode and a front end portion of the center electrode, wherein the spark plug further comprises: a molten layer in which a metal material of a nickel-based plating layer applied to at least a center-electrode-side part of the portion of the ground electrode to be bent and a metal material of the ground electrode are molten together by irradiation with a laser beam or electron beam on the center-electrode-side part of the portion of the ground electrode to be bent; and a nickel-based plating layer on a part of the ground electrode other than the part irradiated with the laser beam or electron beam, wherein a maximum length between a point of a surface of the plating layer closest to the molten layer and a point of the molten layer opposite from the surface of the plating layer in a thickness direction of the ground electrode is 200 μm or smaller.