The inverse correlation of appendectomy and ulcerative colitis is well known, but the effect of appendectomy on the clinical course of ulcerative colitis remains unclear. Although the majority of opinions were negative for the therapeutic advantage of appendectomy in patients with ulcerative colitis, advocates for positive effect of appendectomy have been proposed in a few case reports and a prospective study from Western countries. We herein report a case of ulcerative colitis who experienced clinical remission after appendectomy for acute appendicitis. The patient was 35 year old male and had been managed with immunosuppressant before appendectomy. The very acute change in clinical course and a long period of remission after appendectomy highly suggest the therapeutic effect of appendectomy for ulcerative colitis.