The present invention relates to: a pharmaceutical composition for preventing or treating arthritis, which comprises synthetic polypeptides; injections for preventing or treating arthritis; and a pharmaceutical composition for inducing differentiation of cartilage cells. Synthetic polypeptides of the present invention consisting of a polypeptide represented by SEQ ID NO: 1 and a polypeptide represented by SEQ ID NO: 2 have activity for recruiting stem cells to an arthritis region, inhibit apoptosis of cartilage cells, and exhibit anti-inflammatory activity and activity for promoting regeneration of cartilage cells. Thus, unlike a conventional arthritis treatment agent, the synthetic polypeptides can improve cartilage damage, can inhibit degenerative changes per se and can, at the same time, exhibit an effect as a stem cell treatment agent, and thereby can be usefully utilized as an arthritis prevention or treatment agent.