Objectives : The purpose of this study is to investigate the effect of Leejung-tang plus Oryung-san Gamibang on functional diarrhea.Method : We treated a 72-year-old male who had severe watery diarrhea and bowel sounds. The patient was treated with Korean medicine including Oryung-san Gamibang from March 31, 2016 to May 23, 2016. Defecation frequency, Bristol stool scale, Bowel sound, Patient's condition were measured.Result : After oriental medical treatment, clinical symptoms of functional diarrhea (defecation frequency, stool form, bowel sounds) were recoverd normally.Conclusions : Leejung-tang plus Oryeong-san Gamibang effects on the functional diarrhea of a patient diagnosed as Deficiency Cold (虛寒). This case study shows that Oryeong-san Gamibang is clinically effective for functional diarrhea. So that, it is helpful in decreasing the symptoms of a patient and in improving quality of life.