SPARK PLUG

To provide a spark plug capable of suppressing dropping of a chip from a base material.SOLUTION: A spark plug comprises: a first electrode having a chip made of a noble metal as a main body, a base material connecting Ni as a main body with the chip via a melting part; and a second electrode opposite to a discharge surface of the chip. The melting part has an overlapping part in which a first boundary surface of the chip and the melting part and a second boundary surface of the base material and the melting part is overlapped in a first direction vertical to the discharge surface. The overlapping part is a cross section passing through a center of gravity of the overlapping part projected to a virtual surface parallel to the radiation surface, and when viewing the cross section vertical to the radiation surface, a content ratio of the noble metal of one end part in the second direction along the radiation surface is higher than 50 mass%, and the content ratio of Ni of the other end part in the second direction is higher than 50 mass%.SELECTED DRAWING: Figure 2 【課題】母材からのチップの脱落を抑制できるスパークプラグを提供すること。【解決手段】スパークプラグは、貴金属を主体とするチップと、Ｎｉを主体としチップと溶融部を介して接続された母材と、を備える第１電極と、チップの放電面に対向する第２電極と、を備え、溶融部は、チップと溶融部との第１界面と、母材と溶融部との第２界面と、が放電面に垂直な第１方向において重なり合う重なり部を有する。重なり部は、放電面に平行な仮想面に投影した重なり部の重心を通る断面であり、且つ、放電面に垂直な断面を見たときに、放電面に沿った第２方向における一端部の貴金属の含有率が５０質量％よりも高く、第２方向における他端部のＮｉの含有率が５０質量％よりも高い。【選択図】図２