Bleeding Meckel's diverticulum tends to be a complication of ectopic gastric mucosa. It has been known that the gastric acid and digestive fluid produced from the ectopic gastric mucosa cause peptic ulcer, which leads to bleeding. When the ectopic gastric mucosa is entirely formed by the pyloric gland, however, ulcer formation may result from factors other than gastric acid and digestive fluid. This is a report of an adult case of bleeding Meckel's diverticulum with ectopic gastric mucosa in whom mechanical stimulation was suggested as a cause of the erosion and ulceration, resulting in bleeding.