Study to Confirm the Safety and Efficacy of CJ-12420 in Patients With Erosive Esophagitis

Inclusion Criteria: 1. Subjects aged between 20 and 75 years 2. Endoscopically confirmed erosive esophagitis as defined by LA Classification Grading System (A-D) within 14 days prior to randomization 3. Subjects who had experienced heartburn and regurgitation within 7 days before visit 1 4. Subjects who is able to understand and follow the instructions and is willing to participate throughout the entire study 5. Subjects who voluntarily signed written informed consent form 6. Subjects who agreed to use medically acceptable contraceptives during the period of study Exclusion Criteria: 1. Subjects who cannot undergo EGD 2. Subjects who have esophageal stenosis, ulcer stenosis, gastroesophageal varices, Barrett's esophagus, active gastric ulcer, gastrointestinal bleeding or malignant tumor confirmed by EGD 3. Subjects who have warning symptoms of malignant gastrointestinal tract such as odynophagia, severe dysphagia, bleeding, weight loss, anemia, or bloody stool 4. Subjects with eosinophilic esophagitis 5. Subjects diagnosed with primary esophageal motility disorder, IBS, IBD, etc. or with suspected IBS in the last 3 months 6. Subjects who have a history of gastric acid suppression surgery or upper gastrointestinal, esophageal surgery 7. Subjects who have AIDS or Hepatitis 8. Subjects who take antipsychotic drugs, antidepressant drug, antianxiety drug 9. Subjects who take gastric acid suppression like PPI within 2 weeks to EGD 10. Subjects who take medications related to reflux esophagitis more than 2 times within 1 weeks to EGD 11. Requirement of persistent daily use of drugs that may cause an ulcer such as nonsteroidal anti-inflammatory drugs(NSAIDs) or aspirin during the course of the study 12. Pregnant or lactating women 13. Subjects with the following clinically significant laboratory abnormalities 14. Subjects with the following clinically significant ECG abnormalities 15. Sollinger-Ellison syndrome patients 16. Subjects with a history of malignant tumor 17. Subjects with a history of clinically significant hepatic, renal, cardiovascular, respiratory, endocrine and CNS system disorder 18. Subjects with a history of hypersensitivity to the active ingredient or excipients of the study drug, etc 19. Scheduled surgery requiring hospitalization or requirement of surgical treatment during study participation 20. Subjects who participated in the other clinical trial within 4 weeks prior to randomization 21. Subjects who are judged unsuitable to participate in the study in the opinion of the investigator