A spark plug for an internal-combustion engine is provided wherein the central and ground electrodes exhibit a long service life and wherein the fatigue strength at high temperatures is improved. The ground electrode is made from an alloy comprised of nickel (Ni) as a primary component, chromium: 20-30% by weight, iron: 7-20% by weight, aluminum: 1-3% by weight, titanium: 0.05-0.5% by weight, manganese: not higher than 0.1% by weight, silicon: not higher than 0.1% by weight, and carbon: not higher than 0.5% by weight. The alloy further includes at least one specific element selected from zirconium, yttrium, neodymium, cerium, lanthanum and samarium. Further, the total content of the specific element group is 5% or more of the aluminum content and is not higher than 1% by weight.