Gastritis cystica polyposa (GCP) is an uncommon lesion that usually develops at the gastroenterostomy site. A 57-year-old man visited a hospital with a complaint of melena. He did not have any surgical history or past medical history. Endoscopy was performed to evaluate the cause of melena, and a polypoid cystic mass in the stomach was found on an endoscopy and endoscopic ultrasonography. The polypoid cystic mass did not show any enhancing solid portion on a computed tomography. The gastric lesion was conclusively confirmed as GCP through endoscopic submucosal dissection. We report a rare case of GCP that occurred in an unoperated stomach.