Recently type 1 diabetes with acute onset and no evidence of islet autoantibodies have been showed as "fulminant type 1 diabetes" and as novel subtype of type 1B diabetes. The study was made progress in Japan. We report a typical case of fulminant type 1 diabetes. A 24 years old male to be in good condition visited our hospital because of flu-like symptom, diarrhea, and abdominal discomfort. He has no medical history and family history of diabetes. The level of plasma glucose is 962 mg/dL, serum ketone body 5.8 mmol/L, arterial blood pH 7.111 and he was diagnosed as diabetic ketoacidosis. Anti-GAD antibody and islet cell antibody were negative and HbA1c is 5.5%. All of them were compatible with the diagnostic criteria of fulminant type 1 diabetes. After the patient has been treated with insulin, his symptoms were improved and abnormal laboratory data were normalized. We report this case with a review of the literature.