A 48-year-old female suffered from severe headache, vomiting, and disturbance of consciousness. On admission, she was somnolent with mild paresis of the left leg. Precontrast computed tomography (CT) scans showed a high-density area in the left sylvian fissure and the posterior horn of the left lateral ventricle. Angiographically, a right middle cerebral artery aneurysm and a basilar artery aneurysm were recognized. Furthermore, on the venous phase of bilateral carotid angiograms, superior sagittal sinus (SSS) thrombosis was recognized. Subarachnoid hemorrhage (SAH) was probably induced by rupture of a dilated vein associated with SSS thrombosis, because high-density area on CT scan and location of the aneurysms were different. The patient was initially treated conservatively. Two months later, craniotomy was performed which did not disclose any trace of hemorrhage around the aneurysms and aneurysms themselves. Postoperatively, acute brain swelling and generalized convulsion were induced. The patient became ambulatory 5 months after surgery. In SAH cases, the venous phase should be examined at least in one side of the carotid arteries. In such a SAH case induced by venous thrombosis complicated by aneurysms it is very difficult to decide the timing of surgery for aneurysms.