A method for ameliorating and/or preventing cancerous anemia includes administering to a subject in need thereof an agent containing 5-aminolevulinic acid (ALA) or a derivative thereof, or a salt thereof. Preferably, these ALAs contain a metal-containing compound, such as sodium ferrous citrate. The above-mentioned ALAs, ALA; various esters such as ALA methylester, ALA ethylester, ALA propylester, ALA butylester, and ALA pentylester; and hydrochlorides, phosphates, and sulfates, and the like of these ALA esters are preferred examples.