The purpose of this study is to verify the superior efficacy of Z-338 to placebo in subjects with Functional Dyspepsia, focusing on the assessment of subjective symptoms.

Inclusion Criteria:

• Subjects showing at least one of the 4 symptoms (upper abdominal pain, upper abdominal discomfort, epigastric pain, epigastric burning) for at least 6 months before obtaining informed consent
• Subjects showing two or more of the following symptoms: upper abdominal pain, upper abdominal discomfort, post-prandial fullness, upper abdominal bloating, early satiety, nausea, vomiting and/or excessive belching for at least 3 months (one of them should be post-prandial fullness or early satiation)
• Bothersome symptoms should be post-prandial fullness, upper abdominal bloating or early satiety at the time of obtaining informed consent

Exclusion Criteria:

• Subjects with structural disease that is likely to explain the symptom (e.g., GERD, erosion, ulcer, hiatal hernia, bleeding, malignancy or Barrett's esophagus) confirmed by upper endoscopy at the obtaining informed consent
• Subjects have heartburn in last 12 weeks before obtaining informed consent
• Subjects with irritable bowel disease (IBS)
• Subjects with diabetes mellitus requiring treatment
• Subjects with serious anxiety disorder
• Subjects with depression and/or sleep disorder
• Subjects with biliary tract disease and/or pancreatitis (including chronic pancreatitis)