We experienced a patient with an ileal artificial anus who suffered from abdominal pain caused by peritoneal dissemination of ovarian cancer, for which slow-release oxycodone was ineffective, but fentanyl patch proved effective. The patient was a 28-year-old female who developed abdominal pain caused by peritoneal dissemination on postoperative day 60 after radical hysterectomy and colostomy. For pain relief, administration of 10-mg slow-release oxycodone and 180-mg loxoprofen sodium was begun. When the dose was increased to 25 mg on postoperative day 240, the slow-release oxycodone in its original form was confirmed in feces from the artificial anus.When the same drug was changed to a fentanyl patch(12. 5 mg/hr), the pain was relieved. A palliative care doctor needs much knowledge regarding the changes in the patient's body with the progress and treatment of cancer, in addition to the drug mechanism.