The present invention relates to a composition for promoting peripheral nerve cell proliferation comprising a protein secreted from mesenchymal stem cells, and a medium composition for promoting peripheral nerve cell proliferation comprising the protein. Also, the present invention relates to a method for promoting peripheral nerve cell proliferation using the protein secreted from the mesenchymal stem cells, a peripheral nerve cell of which proliferation is promoted thereby, and a cell therapeutic agent comprising the peripheral nerve cells. The protein secreted from the mesenchymal stem cells according to the present invention can effectively proliferate the peripheral nerve cells, especially Schwann cells, and enables mass production of peripheral nerve cells that can be used as an agent for cell therapy, and thus, is expected to be effective in the development of a therapeutic agent effective for neurological diseases.