Double filtration plasmapheresis (DFPP) is often performed as a treatment for autoimmune diseases including pemphigus vulgaris. We report a pemphigus vulgaris patient with subcutaneous bleeding, gradually spreading over a period of 10 days after DFPP. In this patient, factor XIII activity was markedly decreased. In three other patients, factor XIII activities were markedly reduced the day following DFPP, were but restored by days 7-10. From these findings, subcutaneous bleeding may have occurred in the present patient due to a delayed recovery of the decreased factor XIII activity after DFPP. Therefore, decreased factor XIII activity could be a critical cause of subcutaneous bleeding after DFPP.