We treated a patient with idiopathic cranial hypertrophic pachymeningitis and elevated serum titer of perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) reactive against myeloperoxidase. This 67-year-old man showed multiple cranial nerve-palsies, central diabetes insipidus (DI), and an intrasellar mass. DI and intrasellar mass had been present for 3 years, and DI had been well controlled by intranasal desmopressin. His nerve-palsies were most likely caused by thickened dura matter detected by the brain MRI. Granuloma may develop in the sella, and MRI findings in our patient are compatible to it. Corticosteroid and oral cyclophosphamide therapy improved his neurological symptoms and serum p-ANCA level with showing good correlation. DI improved temporally for 2 months. Few other cases of hypertrophic pachymeningitis with elevated p-ANCA have been reported, however the etiology is unknown. As p-ANCA antibodies have been detected in many of vasculitides, microvasculitis may be involved in some cases of idiopathic hypertrophic pachymeningitis.