This study will evaluate the effect of Helicobacter pylori eradication therapy on the healing of iatrogenic gastric ulcer caused by endoscopic mucosal resection of gastric neoplastic lesions and is a multicenter, randomized, double blind, and placebo controlled trial.

Inclusion Criteria:

• 30 - 75 years old
• Early gastric cancer (< 3 cm in size, mucosa confined, differentiated type) or gastric adenoma (< 3 cm in size)
• Helicobacter pylori positive

Exclusion Criteria:

• Medication of anti-secretory drugs (proton pump inhibitors, H2-receptor antagonists, antacid, bismuth compound)
• History of Helicobacter pylori eradication
• History of gastric surgery or other cancers
• Major comorbidities
• Medication of ASA, NSAIDS, steroids, anti-coagulants