A cell preparation containing mesenchymal stem cells whose immunosuppression ability is maintained is produced by means of a serum-free or low-serum culture. A method for producing a cell preparation containing mesenchymal stem cells, comprising the steps of: (A) proliferating mesenchymal stem cells in a serum-free medium "A" containing an FGF, a PDGF, a TGF-β, an HGF, an EGF, at least one phospholipid, and at least one fatty acid and (B) screening mesenchymal stem cells whose immunosuppression ability is maintained or improved, from the mesenchymal stem cells thus proliferated in the step (A).
