Evaluate the Efficacy and Safety of Pletaal (Cilostazol) in Subjects With Vasospastic Angina

Inclusion Criteria: 1. Male or female over the age of 20 and under the age of 80 2. Diagnosis of vasospastic angina 3. At least one episode of chest pain weekly during the Amlodipine run in period for 2 weeks Exclusion Criteria: 1. Currently taking or has taken Cilostazol within the last 3 month before the screening. 2. Taking oral antiplatelet agents such as Aspirin, Clopidogrel after Amlodipine run-in period. 3. Oral anticoagulants such as Warfarin within the last a month before the screening. 4. Currently taking any of the following medications or has taken any of the following medications within the last a week before the screening: * Other Calcium channel blockers than Amlodipine * Beta-blocker, or Alpha-blocker * Oral Nitrate, Nicorandil, except sublingual Nitroglycerin as required(PRN) * Vitamin E preparations * Estrogens 5. History of Myocardial infarction or Myocardial infarction by vasospastic angina at screening 6. History of life threatening vasospastic events such as ventricular tachycardia , ventricular fibrillation, or syncope 7. History of stroke, intracranial hemorrhage, or Transient Ischemic Attack(TIA) 8. Hemorrhage (hemophilia, capillary fragility, intracranial hemorrhage, upper gastrointestinal hemorrhage, urinary hemorrhage, hemoptysis, vitreous hemorrhage, etc.) or such tendency (active peptic ulcer, hemorrhagic stroke within past 6 months, a case hemorrhage is suspected by wound for surgery within 3 months, proliferative diabetic retinopathy and uncontrolled hypertension) 9. History of clinically significant hypersensitivity to the substances of Cilostazol, Amlodipine, Nitroglycerin or dihydropyridine 10. Patients with severe aortic valvular stenosis 11. History of shock 12. Hypotension of diastolic pressure \< 90 mmHg at screening 13. History of clinically significant hypersensitivity to the substances of Nitrates 14. Patients with severe anemia of Hemoglobin ≤ 6.5 g/dl at screening 15. History of glaucoma 16. Electrocardiogram(ECG) abnormality precluding interpretation of ST change at screening 17. Congestive heart failure with less than 40% of left ventricular ejection fraction within the last 3 month before the screening or screening period 18. Atrial fibrillation or valvular heart disease, more than moderate severity 19. Suspected or identified spasm of left main coronary artery, result of coronary angiography or coronary angiography in the ergonovine induced coronary spasm provocation test 20. History of Coronary artery bypass graft(CABG) or percutaneous coronary intervention(PCI) 21. Tachycardia; Heart rate \> 100 bpm, at Screening 22. Uncontrolled hypertension, defined as ≥ 160 mmHg systolic or ≥ 100 mmHg diastolic at Screening 23. Creatinine ≥ 1.5 mg/dL at screening 24. Aspartate transaminase (AST) or alanine transaminase (ALT) \> 3 times the upper limit of normal (ULN) at screening 25. Platelet \< 100,000 mm3 at screening 26. QT prolongation defined as baseline QTc \> 450 msec for males or \> 470 msec for females at Screening. 27. Women who have the possible of pregnancy, or positive urine or blood pregnancy test at screening 28. Women who are not using a reliable method of birth control, who are pregnant, or who are breast-feeding 29. Drug compliance of Amlodipine \< 80% during the Amlodipine run in period for 2 weeks 30. Otherwise judged by the investigator to be inappropriate for inclusion in the trial.