A 31-year-old man was referred to our hospital because of a chest X-ray abnormality. Computed tomography showed an extra-pulmonary mass along the left 8th rib. T1-weighed magnetic resonance imaging (MRI) revealed a mass lesion with intermediate signal intensity. T2-weighed MRI showed a high signal intensity in peripheral and multiple central portions with intermediate signal intensity, which yielded a bead-like appearance. Gadopentetate dimeglumine-enhanced T1-weighted MRI showed marked contrast enhancement in the central zone of the mass. En bloc resection of the mass with the left 8th rib was performed. The tumor resembled a rosary in gross appearance, and histological examination confirmed the diagnosis of a benign schwannoma arising from the intercostal nerve. The bead-like appearance in the MRI was unique and had never been reported before for such a tumor. The postoperative course was uneventful, and the patient has been well for eighteen months.