SPARK PLUG

[Objective] To provide a technique for enhancing the heat transfer performance of a fusion portion and a noble metal tip. [Means for Solution] A spark plug has a center electrode having an electrode base member and an inner layer which is disposed in the electrode base member and which predominantly contains copper, and a noble metal tip disposed at a forward end of the center electrode, and a fusion portion formed between the noble metal tip, and the electrode base member and the inner layer. The fusion portion is in contact with the inner layer in a cross section which is parallel to the center axis of the center electrode and which passes through the center axis and the fusion portion. The fusion portion contains a component of the noble metal tip, a component of the electrode base member, and a copper component forming the inner layer.