A 42-year-old female patient had been receiving medication for hypertension. Her symptoms worsened in 2007. A computed tomography image revealed a 2.5 cm round mass in the right adrenal gland. According to a careful examination, the patient was diagnosed with primary aldosteronism and subclinical Cushing's syndrome. There were no remarkable physical features related to Cushing's syndrome. The patient chose a medical therapy instead of surgery. In 2012, regardless of strict diet therapy, however, the patient gained 10 kg weight in a year. The diagnosis was the same as that determined in 2007, except for exceeding value of cortisol over the criterion for Cushing's syndrome. A laparoscopic right adrenalectomy was performed to attenuate Cushing's syndrome. The histopathological examination revealed an adrenocortical adenoma. The patient lost 4.5 kg of weight 2 months after the surgery.