Provided is a production method which enables the purification of hematite having a low sulfur component content from an iron-oxide-containing leach residue produced in an HPAL process to such an extent that the hematite can be used as an iron-making raw material. A method for purifying iron oxide for iron-making use in a process comprising adding sulfuric acid to a nickel oxide ore and allowing nickel to be leached out from the nickel oxide ore using a pressurized container, said method being characterized in that the amount of the sulfuric acid to be added is 150 to 220 Kg inclusive relative to 1 ton of the nickel oxide ore.