The present invention relates to a method for isolating umbilical cord-derived stem cells, and more specifically to a method for isolating a significantly large number of mesenchymal stem cells from the umbilical cord having a specified size. The method of the present invention has a great advantage in that since stem cells can be isolated from an umbilical cord tissue without enzymatic treatment, stress applied to the cells can be significantly suppressed. In addition, stem cells obtained by the method of the present invention have superior proliferative capacity compared to stem cells obtained by conventional isolation methods.