A spark plug for use in an internal combustion engine. The spark plug is equipped with a metal shell, a ground electrode joined to the metal shell, and a center electrode disposed in the metal shell. The ground electrode has a protrusion formed on a top end thereof. The metal shell and the ground electrode are covered with a plated layer which has a thickness of 2 μm to 18 μm, which minimizes the possibility of peeling of the plated layer from the ground electrode while keeping the plated layer as thin as possible without sacrificing the resistance to corrosion on the ground electrode.