Cutaneous angiosarcoma is a very rare but aggressive tumor. Angiosarcoma of the scalp is very rare, and a review of the world literature revealed less than 60 cases. Here, the author reports a case of poorly differentiated angiosarcoma of the scalp. The pathological diagnosis was very difficult. A 70-year-old Japanase man was admitted to our hospital complaining of red mass of the scalp. An excisional biopsy was done. The biopsy showed proliferation of malignant spindle cells in the dermis. Apparent differentiation was not recognized. Invasion into the lateral dermis and subcutis was recognized. There were many mitotic figures and a few foci of necrosis. The size was 2 x 2 x 3 cm. Intracytoplasmic vacuoles were recognized in the malignant tumor cells in some places. A few vague vasoformative features were recognized in one very small area. Immunohistochemically, the malignant spindle cells were positive for factor VIII-related antigen (F-VIII-RA), Ulex lectin, CD31, CD34, vimentin, p53 protein. The Ki-67 labeling was 76%. In contrast, the tumor cells were negative for cytokeratins, epithelial membrane antigen, desmin, S100 protein, alpha-smooth muscle antigen, bcl-2, melanosome, and myoglobin. The intracytoplasmic vacuoles were strongly positive for F-VIII-RA, Ulex lectin, CD31, and CD34, The abortive vasoformative channels were moderately positive for these endothelial markers. A pathologic diagnosis of angiosarcoma of the scalp was made. Chemoradiation and immunotherapy were performed. However, the tumor recurred several times, and ultimately metastasized to the systemic bones and lungs. The patient died of systemic carcinomatosis 33 months after the first manifestation.