A brain lesion located at the lateral side of the sella turcica can produce a junctional scotoma by compressing the ipsilateral optic nerve and the contralateral inferonasal nerve fiber. This study reports a female patient with a junctional scotoma caused by a cerebral aneurysm. At the initial visit, she complained of visual disturbance in both eyes and the right optic disc was atrophied. The visual field showed right blindness and left superotemporal quadrantopsia. A brain CT indicated an approximately 3 cm sized brain mass located superolateral to the sella turcica. The brain MRI showed the lesion to be more like an aneurysm than a pituitary adenoma. Therefore, 4 vessels angiography was done, and this lesion was confirmed to be a sellar variant of an aneurysm located at the right carotid siphon. Like a tumor of the optic chiasm, a cerebral aneurysm can cause visual disturbance and visual field defects. Therefore, an early differential diagnosis is important because the prognosis and treatment of an aneurysm differ.