SPARK PLUG AND PRODUCTION METHOD THEREFOR

Disclosed is a spark plug having a ground electrode with tip joint strength and spark wear resistance. A weld zone has: a back region exposed at an opposite surface of an electrode base; a joint region at which a tip is joined; and a connection region connects the joint region and the back region in a thickness direction of the electrode base without being exposed at side surfaces of the electrode base. In a cross section of the ground electrode taken through the side surfaces of the electrode base along a plane passing through the centers of the top and bottom surfaces of the tip, a value of a width of the top surface of the tip being divided by a width of the facing surface of the electrode base is greater than 0.3, and a maximum width of the connection region in a direction perpendicular to the thickness direction of the electrode base is larger than a width of the back region. The joint strength of the tip can be attained by ensuring the joint area. The spark wear resistance of the ground electrode can be attained as the exposed back region of the weld zone is present on the opposite surface at which spark discharge is unlikely to occur.