We report a rare case of primary meningeal malignant melanoma in a 23-year-old female. The patient was admitted to our hospital for sudden onset of consciousness disturbance. Prominent nevi were observed on her trunk. From the spinal fluid, a small number of tumor cells, highly suggestive of malignant lymphoma were evident. However, final cytological diagnosis could not be completed. The cells showed no definitive melanin pigment whatsoever. Shortty there after, biopsy specimens taken during decompression surgery revealed a small number of atypical cells in the specimen containing definitive melanin pigment with vivid nucleoli. These findings lead us to a final diagnosis of malignant melanoma. Special staining i.e. Grimelius, Fontana-Masson and immunostains such as NSE, and S-100 protein supported the diagnosis. Ultrastructural study demonstrated abundant mature melanosomes. Finally, autopsy findings revealed neither metastasis nor lesions indicating another primary focus.