Background : Sulfasalazine for treating ulcerative colitis has a clinical limitation due to its adverse effects. This case is about a patient with ulcerative colitis who could not tolerate sulfasalazine and was improved by Do-che decoction-based Korean medicine. Method and Results : Purulent and bloody diarrhea more than 20 times a day, mild fever, chilling and tenesmus were main symptoms of this patient who was diagnosed as ulcerative colitis 10 years ago. Do-che decoction-based Korean medicine which was recommended for purulent and bloody diarrhea in Dong-Ui-Bo-Gam, the classic literature of Traditional Korean Medicine was given to the patient for more than 1 month. After treatment, the frequency of purulent and bloody diarrhea, tenesmus and fever was decreased remarkably, and C-reactive protein, erythrocyte sedimentation rate, white blood cell count and maximum temperature also dropped to the normal range. Conclusion : Do-che decoction-based Korean medicine has a potential effect and may be a alternative therapeutic option in patients with ulcerative colitis who cannot tolerate sulfasalazine due to its adverse effects.