The present invention relates to a method and an apparatus for fixing carbon dioxide. Provided are a method for fixing carbon dioxide and an apparatus for fixing carbon dioxide, the method comprising the steps of: providing iron manufacturing waste; concentrating the iron manufacturing waste; dehydrating the concentrated iron manufacturing waste; mixing and stirring the dehydrated iron manufacturing waste and a strong acid to separate the generated hydrogen and precipitates; injecting alkali waste water and exhaust gas containing carbon dioxide into the separated precipitates to prepare a carbonate, and preparing a metal carbonate (FeCO3) by the substitution of the carbonate and the precipitates; and drying the metal carbonate (FeCO3).