A 44-year-old man presented with a rare case of idiopathic hypertrophic cranial pachymeningitis manifesting as generalized seizure. Neuroimaging and pathological examinations showed the typical features of hypertrophic cranial pachymeningitis. Tuberculosis was a possible cause based on the positive purified protein-derived skin test, but the origin of the disease was not confirmed by further examinations. Cerebral angiography showed total occlusion of the dural sinuses with development of the emissary veins. Histological examination of the dura showed thickening of the fibrous tissue with rare inflammatory cells, suggestive of the extremely long duration of the disease. The diagnosis was idiopathic hypertrophic cranial pachymeningitis, but was treated only with anticonvulsants. The disease did not progress during follow up of 3 years. Idiopathic hypertrophic cranial pachymeningitis may have various causes related to unusual forms of infectious or autoimmune disorders.