A method for refining fuel oil comprises subjecting fuel oil to an extraction treatment with an extraction agent to extract a light component from the fuel oil, so as to obtain a light oil mixture containing the light component of the fuel oil and the extraction agent. The extraction agent is selected from the group consisting of a matter composed of oil and miscible with the light component of the fuel oil, a non-polar compound in a gaseous state at the room temperature and atmospheric pressure, and a combination thereof. The extraction agent is in a liquid state during the extraction treatment.