Intussusception is a serious disease where part of the intestine slides into an adjacent part of the intestine. Adult intussusception is mainly due to benign or malignant neoplasm. Therefore, in most cases of adult intussusception, treatment by surgery would be preferable to conservative therapy. However, we report on a 28-year-old female patient who underwent intussusception operation delayed 3 months. Abdominal computed tomography 3 months ago showed a small bowel intussusception measuring 20 cm long. Three months later, the previously identified small bowel intussusception appeared without change. The patient underwent surgery, and ectopic gastric mucosa was observed in the biopsy. Therefore, Meckel's diverticulum was diagnosed.