We report a radiation-associated angiosarcoma(RAAS)of the breast, which is a rare but important complication after breast-conserving surgery(BCS)and radiotherapy(RT)for breast cancer. A7 2-year-old woman had undergone BCS for invasive ductal carcinoma of the right breast(pT2pN1M0, StageⅡB), followed by RT of 50 Gy; she was treated with doxifluridine and anastrozole for 5 year. She noticed a bloody cutaneous bulla in the right breast 64 months later, and the skin lesions gradually expanded. She was brought to our clinic for the treatment of massive bleeding from the skin lesions. Ulcer biopsy revealed cutaneous AS(cells were CD31[+], CD34[+], VEGF[-], and VEGF-R[+]). She underwent mastectomy and latissimus dorsal flap surgery. She died of local recurrence and liver metastasis 13 months later. RAAS is rare, but it should be considered in patients with skin lesions, such as erosion and bloody bulla, after BCS and RT for breast cancer. To our knowledge, only 12 cases of RAAS, including the present case, have been reported in Japan, and we reviewed the Japanese RAAS cases in comparison with those reported in the Western literature.