This is a single-center, randomized, double-blind, placebo-controlled clinical Study to evaluate the efficacy of DA-5204 and proton pump inhibitor combination therapy compared with proton pump inhibitor alone therapy in patients with gastroesophageal reflux Disease.

Gastroesophageal reflux disease is a condition in which reflux of stomach contents into the esophagus causes troublesome symptoms, such as heartburn and acid regurgitation.

Proton pump inhibitors, as acid suppressor, are the agents recommended as the first-line treatment for gastroesophageal reflux disease. However, approximately 20-30% of patients have insufficient effect on this therapy alone.

DA-5204 is a medicine based on Artemisia asiatica 95% ethanol extract. DA-5204 has been administered to treat gastritis and gastric ulcers with antioxidative and cytoprotective actions on gastric mucosal damage. Therefore, we expect DA-5204 to be effective in reflux esophagitis (esophageal mucosal injury).

Inclusion Criteria:

• Age is over 20 years old, under 75 years old, men or women
• Patients diagnosed with erosive esophagitis by gastroscopy
• Signed the informed consent forms

Exclusion Criteria:

• Patients who is impossible to receive gastroscopy
• Patients with esophageal stricture, esophageal varix, Barrett's esophagus, peptic ulcer or gastrointestinal bleeding
• Patients administered with prokinetics, H2 receptor antagonists, proton pump inhibitors, anticholinergic drugs or non-steroid anti-inflammatory drugs prior to study in 4 weeks
• Patients with surgery related to gastroesophageal
• Patients with Zollinger-Ellison syndrome
• Patients with any kind of malignant tumor
• Patients administered with anti-thrombotic drugs
• Patients with significant cardiovascular, pulmonary, heptic, renal, hemopoietic or endocrine system primary disease
• Patients with neuropsychiatric disorder, alcoholism, or drug abuse
• Patients taking other investigational drugs or participating in other clinical studies in 4 weeks.
• Women either pregnant or breast feeding