The combination therapy with multiple antihypertensive drugs is recommended in the patients who are uncontrolled with monotherapy. Diuretics increase the activities of renin-angiotensin-aldosterone system (RAS), and angiotensin receptor blockers (ARB) depress blood pressure potently in the state of increased RAS activities. Thus, the combination therapy with ARB and diuretics is expected to lower the blood pressure synergistically. This combination therapy is also expected to reduce the side effects of each drug. In this study, we will compare the effect and safety of the combination therapies between losartan/amlodipine and fixed dose drug of losartan/hydrochlorothiazide.