We experienced a case of gastric cancer that was prospectively followed up for 8 years. With severe heart disease, the patient did not wish surgery or anticancer drug treatment. After informed consent was obtained, he was followed up for 8 years. He received upper gastrointestinal endoscopy every year, which revealed IIc early gastric cancer, and biopsy showed well differentiated adenocarcinoma. A flat and mildly depressed lesion with redness was observed on endoscopy, exhibiting typical morphology of IIc-type early gastric cancer. The appearance of IIc M cancer was observed macroscopically from 2000 to 2003. Four years later, surface irregularity with ulceration appeared. Then, the whole lesion was elevated, which suggested submucosal invasion, and the tumor exhibited the morphology of IIa + IIc or type 3. The ulcer became deeper and elevated boundaries were formed. Horizontal expansion of the flat lesion was mild, while invasion to deeper layers was predominant. Eventually, he died of heart failure. Estimated M cancer was observed for about 3 years, followed by invasion to deeper layers. Taken together, this is a valuable case that followed up the manner of invasion to deeper layers over time from early to advanced gastric cancer.