We report a case of aldosterone-producing microadenoma that was correctly diagnosed and thus treated less invasively by laparoscopic adrenalectomy. A 58-year-old woman presented with palpitation and muscular weakness. She exhibited hypertension, hypokalemia and increased aldosterone excretion with suppressed renin activity. Therefore, primary aldosteronism was suggested. Although adrenal scintigram and computed tomography findings in the adrenal glands were normal, adrenal venous sampling tests indicated an overproduction of aldosterone in the right adrenal gland. We diagnosed an aldosterone-producing microadenoma in the right adrenal gland and performed an adrenalectomy. The patient became normotensive postoperatively and histopathological examination demonstrated a microadenoma, 5 mm in diameter.