Disclosed is a method for culturing mesenchymal stem cells, comprising culturing mesenchymal stem cells in a medium containing calcium in a concentration of from 2.1 to 3.8 mM and magnesium in a concentration of from 1.0 to 3.0 mM under a hypoxic condition of 2 to 5% oxygen. The culturing method can increase the population of mesenchymal stem cells even with a small number of passages by improving mesenchymal stem cells in proliferative capacity and viability. In addition, the mesenchymal stem cells prepared by the culturing method are effectively used to treat or improve a pulmonary disease.