A 57-year-old woman was admitted to our hospital with a complaint of left supraclavicular lymph node's swelling in January 2007. Computed tomography (CT) showed the lobulated tumor suspected of superior vena cava (SVC) invasion, located in the anterior mediastinum, 5 x 3 cm in size. The patient underwent thymectomy, resection of SVC, and partial resection of the right upper lobe. SVC was reconstructed by ready-made Y-graft (Hemashied phi 18 x 9 mm). Histopathological diagnosis was thymic cancer, poorly differentiated squamous cell carcinoma. The patient was discharged on 21st postoperative day. Postoperative radiotherapy (RT : 12.6 Gy) was canceled for the side effect. Alternatively, adjuvant chemotherapy [carboplatin (CBDCA) +paclitaxel (PTX)] was administered. Additional RT (50 Gy) was given to the lesion of local recurrence 1 and half year after the operation. The patient was alive without any signs of recurrence after RT. Left side bypass graft was patent at 8 months postoperatively, but was obliterated thereafter. Right side bypass is patent at more than 2 years postoperatively. Ready-made Y-graft can be one of the choices of SVC reconstruction.