H. pylori is a definite carcinogen of gastric cancer. Animal studies have revealed that primary prevention of gastric cancer by H. pylori eradication is more effective as the duration between H. pylori infection and H. pylori eradication is decreased. In human, the cohort studies showed H. pylori eradication reduced the incidence of gastric cancer in the case with high incidence rate of gastric cancer. In a multi-center, randomized controlled study, H. pylori eradication prevented the incidence of metachronous cancer after endoscopic resection of early gastric cancer. Meta-analysis of RCT suggested that the incidence of gastric cancer was suppressed by H. pylori eradication. The strategy for elimination of gastric cancer in Japan should consist of H. pylori eradication as primary prevention and surveillance of gastric cancer using endoscopy as secondary prevention.