A 67-year-old man had a clinic-based screening by periodic chest radiographs, and one lung nodule was found in the upper lung field. He had a thorough examination and was first diagnosed with stage IV adenocarcinoma of the lung because of adrenal metastasis. He then underwent chemotherapy and was attacked with cardiogenic shock on the day following chemotherapy. Exhibiting dyspnea and disturbance of consciousness, he was transferred to our hospital by ambulance. He was successfully treated with intensive therapy and had the second examination of an isolated enlarged adrenal tumor. This revealed that he had pheochromocytoma with stage IA lung cancer. Surgical resection for pheochromocytoma was performed initially, and he then underwent stereotactic radiotherapy for the lung cancer. During the lung cancer examination, when adrenal incidentaloma was found, we should consider that it might be an intercurrent primary adrenal tumor, such as pheochromocytoma, even if the patient has no symptoms.