Inclusion Criteria:

1. Patients aged 20 years or older at time of consent
2. H. pylori-positive patients meeting both of the following criteria:• Assessed as H. pylori-positive by rapid urease test and/or 13C-urea breath test at pre-study examination, • Assessed as H. pylori-antibody-positive by urine-based test after obtaining informed consent
3. Patients endoscopically diagnosed with gastric ulcer meeting the following criteria:• Active (A1- or A2-stage by Sakita/Miwa classification）, • Solitary, • Longitudinal diameter: ->5 mm
4. Patients who have not received proton pump inhibitors (PPIs), antibacterial agents, or antiprotozoal agents within 1 week prior to endoscopy

Exclusion Criteria:

1. Patients who have previously received H. pylori eradication therapy
2. Patients with acute gastric ulcer
3. Patients with linear ulcer
4. Patients with complication of duodenal ulcer (excluding cicatrix)
5. Patients who have undergone upper-GI tract or vagal nerve resection
6. Patients who are unsuitable for pharmacotherapy, e.g., with perforation or pyloric stenosis
7. Patients with gastric ulcer considered likely to induce massive hemorrhage (e.g., with obviously exposed blood vessels at lesion sites)
8. Patients with a history of amoxicillin shock
9. Patients with infectious mononucleosis
10. Patients with severe renal disorders
11. Patients with a history of hypersensitivity to penicillins, clarithromycin, lansoprazole, or rebamipide
12. Patients who have been treated with drugs contraindicated to clarithromycin, such as terfenadine, cisapride, and pimozide
13. Patients who are pregnant, possibly pregnant, lactating, or who desire to become pregnant during the study
14. Patients who are otherwise judged inappropriate for inclusion in the study by the investigator or subinvestigator