Paraganglioma is a rare tumor arising in the paranglion tissue other than the adrenal medulla. The preoperative diagnosis of asymptomatic paraganglioma not causing excessive secretion of catecholamines is made with difficulty. We encountered a woman who was diagnosed as having a paraganglioma based on hypertension induced by operative manipulation. A 49-year-old woman visited the medical department in our hospital because of abdominal discomfort. Since close examination showed a neurogenic retroperitoneal tumor, she was admitted to the department. On laparotomy, a solid tumor (7×3×5cm) was observed between the abdominal aorta and inferior vena cava and was resected. The initiation of tumor detachment induced hypertension, and increase in the cardiac rate, and increases in all catecholamine fractions. Before the termination of tumor resection, the blood pressure decreased, and the catecholamine fraction levels were rapidly normalized. Her clinical course suggested a paraganiglioma, which was confirmed by intraoperative histopathological examination. In functional paraganglioma even in the absence of symptoms, measures against acute changes in hemodynamics during and after operation are necessary.