NOVELTY - One portion and oil component of hydrocarbon in argon gas are made to adsorb to activated carbon. Oxygen amount in argon gas determines whether required set amount is exceeded after reacting with hydrogen, carbon monoxide and hydrocarbon. When oxygen amount in argon gas is less than set amount, oxygen is added such that set amount optionally exceeds. Carbon dioxide and water are produced in state in which oxygen remained by making carbon monoxide, hydrogen, hydrocarbon and oxygen in argon gas react using rhodium as catalyst. Thus, purification of argon gas is carried out.    USE - Purification of argon gas used as furnace atmosphere gas in silicon mono-crystal pulling furnace, ceramic sintering furnace, vacuum-degassing installation for steel manufacture, silicon plasma dissolving apparatus for solar cell and polycrystalline silicon-casting furnace.    ADVANTAGE - The method efficiently and economically removes oxygen, hydrogen, carbon monoxide, hydrocarbon, oil component and nitrogen as impurities from argon gas.    DETAILED DESCRIPTION - One portion and oil component of hydrocarbon in the argon gas are made to adsorb to activated carbon. The oxygen amount in the argon gas determines whether required set amount is exceeded after reacting with hydrogen, carbon monoxide and hydrocarbon. When the oxygen amount in the argon gas is less than the set amount, oxygen is added such that the set amount optionally exceeds. Carbon dioxide and water are produced in the state in which oxygen remained by making carbon monoxide, hydrogen, hydrocarbon and oxygen in the argon gas react using rhodium as catalyst. Then, carbon monoxide is added such that the set amount which needs the amount of carbon monoxide in the argon gas since it reacts with all the oxygen that remained is exceeded. Carbon dioxide is produced in the state in which carbon monoxide remained by making oxygen and carbon monoxide in the argon gas react using ruthenium and/or rhodium as a catalyst. The impurities in the argon gas are purified by adsorbing impurities to adsorption agent by pressure-swing-adsorption method. An INDEPENDENT CLAIM is included for purifier.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic structure of purifier.    Activated charcoal-absorbing tower (3)    Reaction apparatus (5)    Reactors (5a,5b)    Water-removal device (6)    Adsorption apparatus (7)