The patient was a 73-year-old man who visited our department with black stools as the chief complaint. Upper digestive tract endoscopy revealed three type 2 lesions in the lesser curvature of the gastric antrum and the gastric angle and the posterior wall of the upper gastric body, which were diagnosed by biopsy as tub2, por, and sig, respectively. Total gastrectomy was performed. The final pathological diagnosis was quintuple gastric cancer with a main lesion of large-cell endocrine carcinoma and four adenocarcinoma sublesions. We report this extremely rare case of gastric endocrine cell carcinoma complicated by adenocarcinoma.