The first Acanthamoeba keratitis was found in 1974, and the first Japanese case was reported in 1988. We devided the clinical features to three stages, and described clinical features in each stage. Diagnosis was suspected from clinical history and features, and definite diagnosis was made by direct examination or culture. We recommended the triple procedures consisted from systemic antifungal drug, topical anti-amoebic eye drops, and surgical debridement of the lesion for optimal treatment of Acanthamoeba keratitis. Prevention must be aimed at education of eye care practitioners and contact lens wearers.