A case of Hirschsprung's disease in an adult was treated in our hospital. A 23-year-old man had been suffering from severe constipation since the childhood, for which proctostomy was recommended but his family disliked it. His bowel function was preserved only with daily enemas or purgatives. After puberty, although constipation tendency continued, he had bowel movement in several days with no drugs until the age of 23. Recently constipation gradually became worse, and he admitted to our hospital complaining abdominal pain and distension. Bariun enema revealed atypical caliber change and dilatation in the oral side of it. Hirschsprung's disease was suspected. The definitive diagnosis was made by anorectal manometry and acetylcholine esterase staining after rectal biopsy. Rectosigmoidectomy according to Duhamel method was performed, and his postoperative course was uneventful.