The present invention provides a method of high-temperature denitration characterized in that NOx in an exhaust gas is reduced at 450.degree. to 800.degree. C. using ammonia as a reducing agent in the presence of a catalyst which comprises zirconium oxide and SO.sub.3 or SO.sub.4.sup.2- and has solid acid strength (Ho) of -11.93 or lower. The present invention also provides a method of high temperature denitration characterized in that NOx in an exhaust gas is reduced at 450.degree. to 800.degree. C. using ammonia as a reducing agent in the presence of a catalyst wherein at least one of tungsten oxide, molybdenum oxide and boron oxide is supported on a carrier comprising zirconium oxide and SO.sub.3 or SO.sub.4.sup.2- and having solid acid strength (Ho) of -11.93 or lower.