A 30-year-old male was referred to our department during the examination and treatment for hypertension, because he had not achieved complete erection since the age of 26 years. After detailed examination, he was diagnosed to be suffering from nodal polyarteritis. Since erectile dysfunction persisted, the patient was hospitalized to investigate the cause of erectile dysfunction. Measurement of the penile brachial index (PBI) and cavernous infusion of papaverine hydrochloride strongly suggested the presence of arterial erectile dysfunction. Internal-pudendal angiography revealed multiple microaneurysms in the bilateral internal pudendal arteries, suggesting that nodal polyarteritis caused arterial erectile dysfunction.