Provided is a method for culturing (a storage method) somatic stem cells which has an extremely low impact on viability and deterioration of differentiation and cell functions, replacing conventionally-implemented freezing preservation methods without using a chemical agent such as DMSO that affects the differentiation function of somatic stem cells. The method for culturing mesenchymal stem cells involves using: an undifferentiated maintenance culture material for somatic stem cells, said material being characterized by containing polysaccharides derived from natural substances, and a culture medium in which the undifferentiated maintenance culture material is dispersed, a culture medium containing somatic stem cells in which somatic stem cells are floating in the aforementioned culture medium; and said polysaccharides derived from natural substances.