This method for producing a cartilage-damage treatment agent includes a propagation step for propagating mesenchymal stem cells in a serum-free medium (A) containing FGF, PDGF, TGF-β, HGF, EGF, one or more phospholipids, and one or more fatty acids; and a mixing step for mixing the mesenchymal stem cells, an isotonic preservative, and a cytoprotective agent after the propagation step. This production method makes it possible to provide a cartilage-damage treatment agent for favorably regenerating cartilaginous tissue.