A spark plug having an insulator with a through hole formed therein in a direction of an axis, a center electrode disposed in a front side of the through hole, a metal terminal disposed in a rear side of the through hole, an electrical connection part arranged in the through hole to establish electrical connection between the center electrode and the metal terminal and a metal shell holding therein the insulator. The electrical connection part has a conductor including a conductive material and at least one kind of Fe-containing oxide material. The Fe-containing oxide material contains at least FeO. The conductor satisfies a relationship of 0.06≦S1/(S1+S2)≦0.46 where, in a cross section taken along the axis, S1 is an area occupied by the conductive material and S2 is an area occupied by the Fe-containing oxide material.