A spark plug has a central electrode and a ground electrode. The central electrode has an electrode base material part and a noble metal chip of a cylindrical shape and is welded on the electrode base material part. A spark discharge is generated between the noble metal chip of the central electrode and the ground electrode when supplying a predetermined voltage to the spark plug. An intermediate region is formed on an overall surface between the electrode base material part and the noble metal chip. The intermediate region has a primary measurement part and a secondary measurement part. Components of the noble metal chip in the primary measurement area have a first average ratio of not less than 40 wt %, and components of the noble metal chip in the secondary measurement area have a second average ratio of not more than 80 wt %.