Patent ID: 8298030

Claim:
A manufacturing method of a spark plug, the spark plug including: a cylindrical metal shell; a cylindrical ceramic insulator retained in the metal shell; a center electrode retained in the ceramic insulator and extending in an axial direction; and a ground electrode having a rear end portion fixed to the metal shell and a front end portion formed with a protruding region facing a front end portion of the center electrode with a gap left between the protruding region and the front end portion of the center electrode, the ground electrode being of substantially uniform thickness except for an area where the protrusion is formed, the manufacturing method comprising: a press forming step for pressing the whole of a ground electrode material for constituting the ground electrode, so as to form a protruding region on a front end portion of the ground electrode material; and a welding step for, after the press forming step, welding a rear end portion of the ground electrode material to the metal shell.