Patent ID: 8129891

Claim:
A spark plug comprising a center electrode; an insulator which has an axial hole extending along an axial direction and holds the center electrode in the axial hole; a metallic shell which circumferentially surrounds and holds the insulator; and a ground electrode whose base end portion is joined to the metallic shell and which is bent at an intermediate portion thereof between the base end portion and a distal end portion of the ground electrode such that the distal end portion faces a front end portion of the center electrode, wherein a noble metal tip is disposed on the distal end portion of the ground electrode at a position which faces the front end portion of the center electrode, and a spark gap is formed between the front end portion of the center electrode and the noble metal tip, the spark plug being characterized in that the noble metal tip is joined to a top surface of an intermediate member, which is a member separate from the ground electrode, to thereby be united with the intermediate member, and a bottom surface of the intermediate member is joined to the ground electrode, whereby the noble metal tip is fixed to the ground electrode; and the intermediate member has an average hardness higher than an average hardness of a portion of the ground electrode, excluding the intermediate portion.