A spark plug for use in an internal combustion engine has a center electrode, an earth electrode, and an electrode chip formed on at least one of the center electrode and the earth electrode. A spark discharge gap is formed between the center electrode and the earth electrode. The electrode chip has a base section, a chromium rich layer formed on at least a part of the base section, and a diffusion layer formed between the base section and the chromium rich layer. The base section contains chromium within a range of 5 to 45 mass %, an element X within a range of 0.5 to 25 mass %, and a remainder composed of tungsten and unavoidable impurity. The chromium rich layer is larger in content of chromium than the base section. The element X contained in the base section is comprised of at least one of molybdenum, silicon, aluminum and lead.