CKD-495 is a newly developed drug extracted from Cinnamomum cassia Presl. This phase II study assessed the clinical benefits of CKD-495 in the treatment of acute and chronic gastritis. This study randomly assigned 250 patients with endoscopically-proven gastric mucosal erosion to five groups. The groups received either 75 mg or 150 mg of CKD-495, 100 mg of rebamipide, 60 mg of Artemisiae argyi folium 95% ethanol ext. (20 ⟶ 1) (Stillen; Dong-A ST Co., Ltd., Seoul, Korea), or placebo for 2 weeks, respectively. The primary endpoint was the erosion improvement rate, and the secondary endpoints were erosion cure rates, improvement rates of gastrointestinal symptoms, edema, redness, and hemorrhage. Drug-related adverse events were evaluated. The endoscopic erosion improvement rate was significantly higher in the 75 mg CKD-495 group than in the other groups in both the full analysis set (73% vs. 41%, 45%, 52%, 48% for the 75 mg CKD-495, 150 mg CKD-495, placebo, 60 mg Stillen, and 100 mg rebamipide groups, respectively) and the per-protocol set (PPS) (75% vs. 37%, 45%, 51%, 50%). The cure rate of gastric erosion was significantly higher in the 75 mg CKD-495 group than in the other groups. The improvement rates of hemorrhage erosion were significantly higher in the 150-mg CKD-495 group. No significant differences were observed in the safety profiles. No serious adverse events or drug reactions were observed. These results demonstrate that 75 mg of CKD-495 has excellent efficacy for the treatment of endoscopic and symptomatic improvements for acute and chronic gastritis. ClinicalTrials.gov identifier: NCT03437785.