Peptic ulcer is one of the most prevalent diseases in gastrointestinal field. Recently, evolution was made for pathophysiology of peptic ulcer from "no acid, no ulcer" to Helicobacter pylori and non-steroidal anti-inflammatory drugs. The prevalence of peptic ulcer disease is estimated about 10% in Korea, and has declined due to Helicobacter pylori eradication therapy. Peptic ulcer has the cycle of exacerbation and improvement in the clinical course, and has not occasionally any clinical symptom. Helicobacter pylori eradication has made the marked reduction of relapse of peptic ulcer disease. Although nationwide endoscopic screening has enabled accurate diagnosis of peptic ulcer disease, general guideline for diagnosis of peptic ulcer has not made in Korea. Herein, we propose a guideline for the diagnosis of peptic ulcer according to domestic, international clinical studies, and experts opinions with level of evidence and grade of recommendation.