Disclosed is a method for cleaning of the harmful gas, the method comprising mixing harmful gas, discharged from reaction processes using organic metal compounds as the reaction raw materials, with oxygen or air and thereafter bringing the mixture into contact with a catalyst obtained by carrying a noble metal on an inorganic support, a catalyst comprising at least one metal oxide selected from vanadium oxide, chromium oxide, manganese oxide, iron oxide, copper oxide, silver oxide, cobalt oxide and nickel oxide or a catalyst obtained by carrying the metal oxide on an inorganic support, at temperatures between 100° C. and 800° C. to clean the harmful gas. Disclosed also is an apparatus used in the method. The invention ensures that harmful components can be purified in an efficient manner without discharging organic compounds and a large amount of carbon dioxide after the harmful gas is purified, requiring no aftertreatment.