The present invention relates to a pharmaceutical composition for treating diabetes, which includes a pancreatic islet cell and an elastin-like artificial extracellular matrix (REP), and more particularly, to a pharmaceutical composition for treating diabetes, in which pancreatic islet cells are reacted with an elastin-like artificial extracellular matrix and then the resulting cells are administered along with the elastin-like artificial extracellular matrix, thus increasing a survival rate of the transplanted pancreatic islet cells, rapidly restoring a blood glucose level to normal, and maintaining the restored blood glucose level for a long period of time, and, accordingly, diabetes may be more effectively treated.